rcar-gen3: libgbm: Update SRCREV to follow the latest version
rcar-gen3: libgbm: Update SRCREV to follow the latest version

This commit modifies libgbm SRCREV to include some updates
for backend_kms:
- Remove unused variables.
- Fix warnings according to static code analysis tool.

Signed-off-by: Thao Nguyen <5dfc77e0aba37849239cce64b22a9ca173f90e86@renesas.com>
Signed-off-by: Takamitsu Honda <dd018642994e4b3e742377b6d773664f62294df8@renesas.com>

renesas-rcar/meta-renesas,slawr/meta-renesas,slawr/meta-renesas,renesas-rcar/meta-renesas,slawr/meta-renesas,renesas-rcar/meta-renesas,renesas-rcar/meta-renesas