exynos: use structure initialization instead of memset

Keeps the code cleaner, since the structs have to be initialized
once anyway.

Signed-off-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Reviewed-by: Inki Dae <inki.dae@samsung.com>
Tested-by: Joonyoung Shim <jy0922.shim@samsung.com>
[evelikov: squash trivial conflict]
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>

Conflicts:
	tests/exynos/exynos_fimg2d_test.c