Convert CONFIG_SPL_SPI_SUPPORT to Kconfig

Move this option to Kconfig and tidy up existing uses.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/P1010RDB-PA_36BIT_SPIFLASH_defconfig b/configs/P1010RDB-PA_36BIT_SPIFLASH_defconfig
index 3ba484c..94f1501 100644
--- a/configs/P1010RDB-PA_36BIT_SPIFLASH_defconfig
+++ b/configs/P1010RDB-PA_36BIT_SPIFLASH_defconfig
@@ -6,6 +6,7 @@
 CONFIG_SPL_ENV_SUPPORT=y
 CONFIG_SPL_DRIVERS_MISC_SUPPORT=y
 CONFIG_SPL_SPI_FLASH_SUPPORT=y
+CONFIG_SPL_SPI_SUPPORT=y
 CONFIG_MPC85xx=y
 CONFIG_TARGET_P1010RDB=y
 CONFIG_PHYS_64BIT=y