meta-agl-bsp/core: mesa: generic patches should be y-c-l safe

meta-agl-bsp/core: mesa: generic patches should be y-c-l safe

SPEC-4724 added a generic backported patch to mesa. But instead of
adding it directly to mesa_%.bbappend, it should have been added to
mesa_agl.inc which is only active when "aglcore" feature is enabled,
making it yocto-check-layer safe.

Bug-AGL: SPEC-4723

Change-Id: I226cba14de917f6e4109d1dc1df364cb74e7ee45
Signed-off-by: Denys Dmytriyenko <denys@konsulko.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/28741
Reviewed-by: Marius Vlad <marius.vlad@collabora.com>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
Tested-by: Jenkins Job builder account
ci-image-build: Jenkins Job builder account
ci-image-boot-test: Jenkins Job builder account