checkpatch.pl: Make CONFIG_IS_ENABLED(CONFIG_*) an error

CONFIG_IS_ENABLED() takes the kconfig name without the CONFIG_ prefix,
e.g. CONFIG_IS_ENABLED(CLK) for CONFIG_CLK. Make including the prefix
an error in checkpatch.pl so calls in the wrong format aren't
accidentally reintroduced.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 4bed2b0..4ed7e12 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -2365,6 +2365,12 @@
 		ERROR("DISABLE_FDT_OR_INITRD_RELOC",
 		     "fdt or initrd relocation disabled at boot time\n" . $herecurr);
 	}
+
+	# Do not use CONFIG_ prefix in CONFIG_IS_ENABLED() calls
+	if ($line =~ /^\+.*CONFIG_IS_ENABLED\(CONFIG_\w*\).*/) {
+		ERROR("CONFIG_IS_ENABLED_CONFIG",
+		      "CONFIG_IS_ENABLED() takes values without the CONFIG_ prefix\n" . $herecurr);
+	}
 }
 
 sub process {