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/mt7620_mt7530_rfb_defconfig b/configs/mt7620_mt7530_rfb_defconfig
index db69e6f..d6095fa 100644
--- a/configs/mt7620_mt7530_rfb_defconfig
+++ b/configs/mt7620_mt7530_rfb_defconfig
@@ -8,7 +8,7 @@
 CONFIG_ENV_SECT_SIZE=0x10000
 CONFIG_SYS_MALLOC_LEN=0x100000
 CONFIG_DEFAULT_DEVICE_TREE="mediatek,mt7620-mt7530-rfb"
-CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_SERIAL=y
 CONFIG_SPL_SYS_MALLOC_F_LEN=0x40000
 CONFIG_SPL=y
 CONFIG_DEBUG_UART_BASE=0xb0000c00