Convert CONFIG_CMD_ERRATA to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_ERRATA

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/P1021RDB-PC_defconfig b/configs/P1021RDB-PC_defconfig
index c7d109c..53c41b4 100644
--- a/configs/P1021RDB-PC_defconfig
+++ b/configs/P1021RDB-PC_defconfig
@@ -1,5 +1,6 @@
 CONFIG_PPC=y
 CONFIG_MPC85xx=y
+# CONFIG_CMD_ERRATA is not set
 CONFIG_TARGET_P1021RDB=y
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y