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/configs/xilinx_versal_net_mini_qspi_defconfig b/configs/xilinx_versal_net_mini_qspi_defconfig
index c9497bb..4fa83fa 100644
--- a/configs/xilinx_versal_net_mini_qspi_defconfig
+++ b/configs/xilinx_versal_net_mini_qspi_defconfig
@@ -57,6 +57,7 @@
 # CONFIG_I2C is not set
 # CONFIG_INPUT is not set
 # CONFIG_MMC is not set
+CONFIG_MTD=y
 CONFIG_DM_SPI_FLASH=y
 # CONFIG_SPI_FLASH_SMART_HWCAPS is not set
 # CONFIG_SPI_FLASH_LOCK is not set