[media] s5p-fimc: Fix horizontal/vertical image flip

Setting FIMC_REG_CITRGFMT_FLIP_X_MIRROR bit causes X-axis image
flip (vertical flip) and thus it corresponds to V4L2_CID_VFLIP.
Likewise, setting FIMC_REG_CITRGFMT_FLIP_Y_MIRROR bit causes Y-axis
image flip (horizontal flip) and thus it corresponds to V4L2_CID_HFLIP.
Currently the driver does X-axis flip when V4L2_CID_HFLIP is set and
Y-axis flip for V4L2_CID_VFLIP. Fix this incorrect assignment by setting
proper FIMC_REG_CITRGFMT register bits for ctx->hflip and ctx->vflip.

Reported-by: Kyungmin Park <kyungmin.park@samsung.com>
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>