powerpc: select MEMORY for FSL_IFC to not break existing .config files

commit d2ae2e20

 ("driver/memory:Move
Freescale IFC driver to a common driver") introduces this build
regression into the mpc85xx_defconfig:

 drivers/built-in.o: In function `fsl_ifc_nand_remove':
 drivers/mtd/nand/fsl_ifc_nand.c:1147: undefined reference to `fsl_ifc_ctrl_dev'
 drivers/mtd/nand/fsl_ifc_nand.c:1147: undefined reference to `fsl_ifc_ctrl_dev'
 drivers/built-in.o: In function `fsl_ifc_nand_probe':
 drivers/mtd/nand/fsl_ifc_nand.c:1031: undefined reference to `fsl_ifc_ctrl_dev'
 drivers/mtd/nand/fsl_ifc_nand.c:1031: undefined reference to `fsl_ifc_ctrl_dev'
 drivers/built-in.o: In function `match_bank':
 drivers/mtd/nand/fsl_ifc_nand.c:1013: undefined reference to `convert_ifc_address'
 drivers/built-in.o: In function `fsl_ifc_nand_probe':
 drivers/mtd/nand/fsl_ifc_nand.c:1059: undefined reference to `fsl_ifc_ctrl_dev'
 drivers/mtd/nand/fsl_ifc_nand.c:1080: undefined reference to `fsl_ifc_ctrl_dev'
 drivers/mtd/nand/fsl_ifc_nand.c:1069: undefined reference to `fsl_ifc_ctrl_dev'
 drivers/mtd/nand/fsl_ifc_nand.c:1069: undefined reference to `fsl_ifc_ctrl_dev'
 make: *** [vmlinux] Error 1

This happens because there is nothing to descend us into the
drivers/memory directory in the mpc85xx_defconfig.  It wasn't
selecting CONFIG_MEMORY.  So we never built drivers/memory/fsl_ifc.o
and so we have nothing to link the above symbols against.

Since the goal of the original commit was to relocate the driver to
an arch independent location, it only makes sense to relocate the
Kconfig setting there as well.  But that alone won't fix the build
failure; for that we ensure whoever selects FSL_IFC also selects MEMORY.

Cc: Prabhakar Kushwaha <prabhakar@freescale.com>
Cc: Scott Wood <scottwood@freescale.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>