[media] exynos4-is: Use common driver data for all FIMC-LITE IP instances

There is no need to use separate variant data structure for each
FIMC-LITE IP instance. According to my knowledge there are no
differences across them on Exynos4 as well as Exynos5 SoCs. Drop
flite_variant data structure and use struct flite_drvdata instead.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>