OMAPDSS: DISPC: fix usage of dispc_ovl_set_accu_uv

Commit 05dd0f53 ("OMAPDSS: DISPC: Update
Accumulator configuration for chroma plane") adds
dispc_ovl_set_accu_uv() function that sets the accu, but the function
only handles YUV and NV12 modes, and BUGs otherwise.

The patch also adds a call to the function, but unfortunately the place
of call was such that the mode could be other than YUV or NV12, thus
crashing the driver.

This patchs moves the call to a slightly later spot, at which point only
YUV and NV12 modes are handled.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Chandrabhanu Mahapatra <cmahapatra@ti.com>