ARM: exynos_defconfig: Increase CONFIG_CMA_SIZE_MBYTES to 96

ARM: exynos_defconfig: Increase CONFIG_CMA_SIZE_MBYTES to 96

Current CMA size of 64 Mbytes is right on the edge of being small when
several drivers need to allocate large CMA buffers.

For example, if the s5p-mfc driver needs to pre-allocate CMA memory to
decode a H.264 1080p video, then there won't be enough CMA memory left
for other drivers, such as the exynos-drm driver that may need to
allocate GEM buffers for the display manager.

Increasing CMA size to 96 Mbytes in exynos_defconfig addresses use-cases
such as these.

Suggested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>