spi: Rename SPI_SUPPORT to SPI

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/sifive_unmatched_defconfig b/configs/sifive_unmatched_defconfig
index 8ac2385..7d45fbf 100644
--- a/configs/sifive_unmatched_defconfig
+++ b/configs/sifive_unmatched_defconfig
@@ -7,7 +7,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="hifive-unmatched-a00"
 CONFIG_SPL_MMC=y
 CONFIG_SPL=y
-CONFIG_SPL_SPI_SUPPORT=y
+CONFIG_SPL_SPI=y
 CONFIG_TARGET_SIFIVE_UNMATCHED=y
 CONFIG_ARCH_RV64I=y
 CONFIG_RISCV_SMODE=y