Convert CONFIG_SPL_LIBGENERIC_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/ls1021atwr_sdcard_qspi_defconfig b/configs/ls1021atwr_sdcard_qspi_defconfig
index 4e6cb24..9ad9eba 100644
--- a/configs/ls1021atwr_sdcard_qspi_defconfig
+++ b/configs/ls1021atwr_sdcard_qspi_defconfig
@@ -1,6 +1,7 @@
 CONFIG_ARM=y
 CONFIG_TARGET_LS1021ATWR=y
 CONFIG_SPL_LIBCOMMON_SUPPORT=y
+CONFIG_SPL_LIBGENERIC_SUPPORT=y
 CONFIG_SPL_I2C_SUPPORT=y
 CONFIG_SPL_ENV_SUPPORT=y
 CONFIG_DEFAULT_DEVICE_TREE="ls1021a-twr-duart"