package/freescale-imx/imx-gpu-g2d: drop BR2_PACKAGE_IMX_GPU_G2D_EXAMPLES

Arm and aarch64 packages don't contain examples anymore so drop the
config option to install them to prevent build failure when selected:

>>> imx-gpu-g2d 6.4.3.p4.4-arm Installing to target
mkdir -p /home/sszy/br-test-pkg/bootlin-armv7-glibc/target/usr/share/examples/
cp -a /home/sszy/br-test-pkg/bootlin-armv7-glibc/build/imx-gpu-g2d-6.4.3.p4.4-arm/gpu-demos/opt/* /home/sszy/br-test-pkg/bootlin-armv7-glibc/target/usr/share/examples/
cp: cannot stat '/home/sszy/br-test-pkg/bootlin-armv7-glibc/build/imx-gpu-g2d-6.4.3.p4.4-arm/gpu-demos/opt/*': No such file or directory
make: *** [package/pkg-generic.mk:384: /home/sszy/br-test-pkg/bootlin-armv7-glibc/build/imx-gpu-g2d-6.4.3.p4.4-arm/.stamp_target_installed] Error 1

Fixes: b84557b5 ("package/freescale-imx/imx-gpu-g2d: bump version to 6.4.3.p4.4")
Signed-off-by: Sébastien Szymanski <sebastien.szymanski@armadeus.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>