spl: Make SHOW_ERRORS depend on LIBCOMMON

The purpose of SHOW_ERRORS is to print extra information. Make it depend
on LIBCOMMON to avoid having to check for two configs.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/common/spl/Kconfig b/common/spl/Kconfig
index 00332cf..e929f1b 100644
--- a/common/spl/Kconfig
+++ b/common/spl/Kconfig
@@ -183,6 +183,7 @@
 
 config SPL_SHOW_ERRORS
 	bool "Show more information when something goes wrong"
+	depends on SPL_LIBCOMMON_SUPPORT
 	help
 	  This enabled more verbose error messages and checking when something
 	  goes wrong in SPL. For example, it shows the error code when U-Boot