serial: Rename SERIAL_SUPPORT to SERIAL

Rename these options so that CONFIG_IS_ENABLED can be used with them.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/microblaze-generic_defconfig b/configs/microblaze-generic_defconfig
index 8562c87..8db9bac 100644
--- a/configs/microblaze-generic_defconfig
+++ b/configs/microblaze-generic_defconfig
@@ -6,7 +6,7 @@
 CONFIG_ENV_SIZE=0x20000
 CONFIG_SYS_MALLOC_LEN=0xc0000
 CONFIG_DEFAULT_DEVICE_TREE="microblaze-generic"
-CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_SERIAL=y
 CONFIG_SPL=y
 CONFIG_TARGET_MICROBLAZE_GENERIC=y
 CONFIG_XILINX_MICROBLAZE0_USE_MSR_INSTR=1