mtd: Make CONFIG_MTD be the gate symbol for the menu

The help for CONFIG_MTD explains that it needs to be enabled for various
things like NAND, etc to be available. It however then doesn't enforce
this dependency and so if you have none of these systems present you
still need to disable a number of options. Fix this by making places
that select/imply one type of flash, but did not do the same, also do
this for "MTD". Make boards which hadn't been enabling MTD already but
need it now, do so. In a few places, disable CONFIG_CMD_MTDPARTS as it
wasn't previously enabled but was now being implied.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/Kconfig b/arch/Kconfig
index c23d57e..b6fb9e9 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -149,6 +149,7 @@
 	select GZIP_COMPRESSED
 	select IO_TRACE
 	select LZO
+	select MTD
 	select OF_BOARD_SETUP
 	select PCI_ENDPOINT
 	select SPI
@@ -254,6 +255,7 @@
 	imply DM_RTC
 	imply SCSI
 	imply DM_SERIAL
+	imply MTD
 	imply DM_SPI
 	imply DM_SPI_FLASH
 	imply DM_USB