Kconfig: nand: Make MTD_NAND_FSL_ELBC depend on FSL_SOC

MTD_NAND_FSL_ELBC selects FSL_LBC that in turn depends on FSL_SOC, so
depending on PPC instead of FSL_SOC leads to this message:

	  warning: (MPC836x_RDK && MTD_NAND_FSL_ELBC &&
	  MTD_NAND_FSL_UPM) selects FSL_LBC which has unmet direct
	  dependencies (FSL_SOC)

when doing

	  make ARCH=powerpc \
	       CROSS_COMPILE=powerpc-e500v2-linux-gnuspe- \
	       allmodconfig"

Changing dependency to FSL_SOC fixes that.
Signed-off-by: NAndrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: NBoris Brezillon <boris.brezillon@free-electrons.com>

drivers/mtd/nand/Kconfig

@@ -428,7 +428,7 @@ config MTD_NAND_ORION
 
 config MTD_NAND_FSL_ELBC
 	tristate "NAND support for Freescale eLBC controllers"
-	depends on PPC
+	depends on FSL_SOC
 	select FSL_LBC
 	help
 	  Various Freescale chips, including the 8313, include a NAND Flash