ARM: multi_v7_defconfig: Enable Samsung media platform drivers as modules

There are a bunch of media platform drivers under drivers/media/platform/
for Samsung SoCs that are enabled in exynos_defconfig but no in multi_v7.

This patch enables them as a module to improve build coverage for these
drivers and also to allow people use them with proper hardware if modules
are installed.

Suggested-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>