checkpatch: add ignore=STRLCPY

Checkpatch complains over strlcpy:
WARNING: Prefer strscpy over strlcpy - see: KSPP/linux#89

However, OP-TEE doesn't have a strscpy() function to use, so silence the
warning until one is available.

Signed-off-by: Jens Wiklander <[email protected]>
Reviewed-by: Etienne Carriere <[email protected]>

.checkpatch.conf

@@ -8,6 +8,7 @@
 --ignore=FILE_PATH_CHANGES
 --ignore=GERRIT_CHANGE_ID
 --ignore=NOT_UNIFIED_DIFF
+--ignore=STRLCPY
 --ignore=PREFER_KERNEL_TYPES
 --ignore=USLEEP_RANGE
 --kconfig-prefix=CFG_