CRISv32: Select MTDRAM for axisflashmap

Fixes compile error on allmodconfig.
Signed-off-by: NJesper Nilsson <jesper.nilsson@axis.com>

arch/cris/arch-v32/drivers/Kconfig

@@ -108,6 +108,7 @@ config ETRAX_AXISFLASHMAP
 	select MTD_JEDECPROBE
 	select MTD_BLOCK
 	select MTD_COMPLEX_MAPPINGS
+	select MTD_MTDRAM
 	help
 	  This option enables MTD mapping of flash devices.  Needed to use
 	  flash memories.  If unsure, say Y.