mtd: Rename SPL_MTD_SUPPORT to SPL_MTD

Rename SPL_MTD_SUPPORT to SPL_MTD in order to match MTD. This allows using
CONFIG_IS_ENABLED to test for MTD support.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
diff --git a/configs/cm_t43_defconfig b/configs/cm_t43_defconfig
index 73ccefd..1a558b0 100644
--- a/configs/cm_t43_defconfig
+++ b/configs/cm_t43_defconfig
@@ -37,7 +37,7 @@
 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR=0x480
 CONFIG_SPL_FS_EXT4=y
 CONFIG_SPL_I2C=y
-CONFIG_SPL_MTD_SUPPORT=y
+CONFIG_SPL_MTD=y
 # CONFIG_SPL_NAND_SUPPORT is not set
 CONFIG_SPL_NAND_DRIVERS=y
 CONFIG_SPL_NAND_ECC=y