lint: checkpatch: Only exclude specific src/vendorcode/ subdirectories

Some of the src/vendorcode/ directories are used to import a whole
codebase from somewhere else which uses a completely different coding
style. For those directories, excluding them from checkpatch makes
sense. However, other directories are simply implementing
vendor-specific extensions that were written by coreboot developers
specifically for coreboot in coreboot's coding style. Those directories
should be covered by checkpatch.

This patch narrows the existing blanket exception of src/vendorcode/ to
the amd, cavium, intel and mediatek directories (which actually include
large amounts of foreign source). The eltan, google and siemens
directories (which seem to contain code specifically written for
coreboot) will now be covered by checkpatch.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: I1feaba37c469714217fff4d160e595849e0230b9
Reviewed-on: https://review.coreboot.org/c/coreboot/+/51827
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-by: David Hendricks <david.hendricks@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

.checkpatch.conf

@@ -32,5 +32,8 @@
 # some commits unnecessarily.
 --ignore EXECUTE_PERMISSIONS
 
-# Exclude the vendorcode directory
---exclude src/vendorcode
+# Exclude vendorcode directories that don't follow coreboot's coding style.
+--exclude src/vendorcode/amd
+--exclude src/vendorcode/cavium
+--exclude src/vendorcode/intel
+--exclude src/vendorcode/mediatek

util/lint/lint-007-checkpatch

@@ -15,7 +15,6 @@ EXCLUDED_DIRS="^payloads/libpayload/util/kconfig\|\
 ^util/inteltool\|\
 ^util/kconfig\|\
 ^util/superiotool\|\
-^src/vendorcode\|\
 ^Documentation"
 
 opts="--max-line-length 96"