m68knommu: only set CONFIG_ISA_DMA_API for ColdFire sub-arch

> Hi Arnd,
>
> First bad commit (maybe != root cause):
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> head:   2f73937c9aa561e2082839bc1a8efaac75d6e244
> commit: 47fd22f2b8 [4771/5318] cs89x0: rework driver configuration
> config: m68k-randconfig-c003-20210804 (attached as .config)
> compiler: m68k-linux-gcc (GCC) 10.3.0
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=47fd22f2b84765a2f7e3f150282497b902624547
>         git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
>         git fetch --no-tags linux-next master
>         git checkout 47fd22f2b8
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-10.3.0 make.cross ARCH=m68k
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
> All errors (new ones prefixed by >>):
>
>    In file included from include/linux/kernel.h:19,
>                     from include/linux/list.h:9,
>                     from include/linux/module.h:12,
>                     from drivers/net/ethernet/cirrus/cs89x0.c:51:
>    drivers/net/ethernet/cirrus/cs89x0.c: In function 'net_open':
>    drivers/net/ethernet/cirrus/cs89x0.c:897:20: error: implicit declaration of function 'isa_virt_to_bus'; did you mean 'virt_to_bus'? [-Werror=implicit-function-declaration]
>      897 |     (unsigned long)isa_virt_to_bus(lp->dma_buff));
>          |                    ^~~~~~~~~~~~~~~
>    include/linux/printk.h:141:17: note: in definition of macro 'no_printk'
>      141 |   printk(fmt, ##__VA_ARGS__);  \
>          |                 ^~~~~~~~~~~
>    drivers/net/ethernet/cirrus/cs89x0.c:86:3: note: in expansion of macro 'pr_debug'
>       86 |   pr_##level(fmt, ##__VA_ARGS__);   \
>          |   ^~~
>    drivers/net/ethernet/cirrus/cs89x0.c:894:3: note: in expansion of macro 'cs89_dbg'
>      894 |   cs89_dbg(1, debug, "%s: dma %lx %lx\n",
>          |   ^~~~~~~~
> >> drivers/net/ethernet/cirrus/cs89x0.c:914:3: error: implicit declaration of function 'disable_dma'; did you mean 'disable_irq'? [-Werror=implicit-function-declaration]

As far as I can tell, this is a bug with the m68kmmu architecture, not
with my driver:
The CONFIG_ISA_DMA_API option is provided for coldfire, which implements it,
but dragonball also sets the option as a side-effect, without actually
implementing
the interfaces. The patch below should fix it.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>

arch/m68k/Kconfig.bus

@@ -63,7 +63,7 @@ source "drivers/zorro/Kconfig"
 
 endif
 
-if !MMU
+if COLDFIRE
 
 config ISA_DMA_API
 	def_bool !M5272