binfmt_flat: add a ARCH_HAS_BINFMT_FLAT option

Allow architectures to opt into ARCH_HAS_BINFMT_FLAT support instead of
assuming that all nommu ports support the format.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>
diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig
index f11433d..d411de0 100644
--- a/arch/microblaze/Kconfig
+++ b/arch/microblaze/Kconfig
@@ -3,6 +3,7 @@
 	def_bool y
 	select ARCH_32BIT_OFF_T
 	select ARCH_NO_SWAP
+	select ARCH_HAS_BINFMT_FLAT if !MMU
 	select ARCH_HAS_DMA_COHERENT_TO_PFN if MMU
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_SYNC_DMA_FOR_CPU