Convert CONFIG_SPL_LIBCOMMON_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/corvus_defconfig b/configs/corvus_defconfig
index 59fffb5..e08f430 100644
--- a/configs/corvus_defconfig
+++ b/configs/corvus_defconfig
@@ -2,6 +2,7 @@
 CONFIG_ARCH_AT91=y
 CONFIG_TARGET_CORVUS=y
 CONFIG_SPL_GPIO_SUPPORT=y
+CONFIG_SPL_LIBCOMMON_SUPPORT=y
 CONFIG_DEFAULT_DEVICE_TREE="at91sam9g45-corvus"
 CONFIG_SYS_EXTRA_OPTIONS="AT91SAM9M10G45,MACH_TYPE=2066,SYS_USE_NANDFLASH"
 CONFIG_BOOTDELAY=3