mtd: add arch dependency for MTD_BCM47XXSFLASH symbol

We dropped strict MIPS dependency for bcm47xxsflash driver in:
commit 5651d6aa ("mtd: bcm47xxsflash: use ioremap_cache() instead of
KSEG0ADDR()") but using ioremap_cache still limits building it to few
selected architectures only.

A recent commit 57d8f7dd ("bcma: allow enabling serial flash support
on non-MIPS SoCs") automatically dropped MIPS dependency for
MTD_BCM47XXSFLASH which broke building e.g. on powerpc and cris.

The bcma change is alright as it doesn't break building bcma code in any
way. MTD_BCM47XXSFLASH on the other hand should be limited to archs
which need it and can build it (by providing ioremap_cache).

Fixes: 57d8f7dd ("bcma: allow enabling serial flash support on non-MIPS SoCs")
Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Cc: Brian Norris <computersforpeace@gmail.com>
Acked-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/mtd/devices/Kconfig

@@ -114,7 +114,7 @@ config MTD_SST25L
 
 config MTD_BCM47XXSFLASH
 	tristate "R/O support for serial flash on BCMA bus"
-	depends on BCMA_SFLASH
+	depends on BCMA_SFLASH && (MIPS || ARM)
 	help
 	  BCMA bus can have various flash memories attached, they are
 	  registered by bcma as platform devices. This enables driver for