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/phycore-am335x-r2-wega_defconfig b/configs/phycore-am335x-r2-wega_defconfig
index 6060754..b91b966 100644
--- a/configs/phycore-am335x-r2-wega_defconfig
+++ b/configs/phycore-am335x-r2-wega_defconfig
@@ -28,7 +28,7 @@
 CONFIG_SPL_SYS_MALLOC=y
 CONFIG_SPL_SYS_MALLOC_SIZE=0x800000
 CONFIG_SPL_I2C=y
-CONFIG_SPL_MTD_SUPPORT=y
+CONFIG_SPL_MTD=y
 CONFIG_SPL_NAND_DRIVERS=y
 CONFIG_SPL_NAND_ECC=y
 CONFIG_SPL_NAND_BASE=y