checkpatch.conf: Ignore check for pointer comparisons to NULL

Change-Id: I1e0c4470bf946285d6af3c8b2f143982bc335159
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/67697
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

.checkpatch.conf

@@ -4,6 +4,7 @@
 # Ignore aspects we don't follow here.
 --ignore C99_COMMENTS
 --ignore GLOBAL_INITIALISERS
+--ignore COMPARISON_TO_NULL
 --ignore INITIALISED_STATIC
 --ignore LINE_SPACING
 --ignore NEW_TYPEDEFS