riscv: only select GENERIC_IOREMAP if MMU support is enabled

nommu ioremap is an inline stub in asm-generic/io.h.

Link: https://lkml.kernel.org/r/20210825072036.GA29161@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/riscv/Kconfig

@@ -48,7 +48,7 @@ config RISCV
 	select GENERIC_CLOCKEVENTS_BROADCAST if SMP
 	select GENERIC_EARLY_IOREMAP
 	select GENERIC_GETTIMEOFDAY if HAVE_GENERIC_VDSO
-	select GENERIC_IOREMAP
+	select GENERIC_IOREMAP if MMU
 	select GENERIC_IRQ_MULTI_HANDLER
 	select GENERIC_IRQ_SHOW
 	select GENERIC_LIB_DEVMEM_IS_ALLOWED