m68k: /proc/hardware should depend on PROC_FS

When CONFIG_PROC_FS is not set, there is a build error for an unused
function. Make PROC_HARDWARE depend on PROC_FS to prevent this error.

In file included from ../arch/m68k/kernel/setup.c:3:
../arch/m68k/kernel/setup_mm.c:477:12: error: 'hardware_proc_show' defined but not used [-Werror=unused-function]
  477 | static int hardware_proc_show(struct seq_file *m, void *v)
      |            ^~~~~~~~~~~~~~~~~~

Fixes: 66d857b08b ("m68k: merge m68k and m68knommu arch directories") # v3.0
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/20230209010825.24136-1-rdunlap@infradead.org
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

arch/m68k/Kconfig.devices

@@ -19,6 +19,7 @@ config HEARTBEAT
 # We have a dedicated heartbeat LED. :-)
 config PROC_HARDWARE
 	bool "/proc/hardware support"
+	depends on PROC_FS
 	help
 	  Say Y here to support the /proc/hardware file, which gives you
 	  access to information about the machine you're running on,