vebox: fix invalid conversion and scaling params order.

The arguments to vpp_surface_convert() were mixed up. i.e. both input
and output surfaces were reversed. Changed the vpp_surface_scaling()
arguments order as well to have more consistent helper functions.

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
vebox: clean-up frame store initialization.

Rename FRAME_STORE_SUM to FRAME_STORE_COUNT, use existing macros to
determine the number of elements in the frame store array, avoid
duplicate zero initializations.

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
vebox: factor out initialization of pipeline parameters.

Factor out initialization and validation of pipeline parameters.
In particular, introduce a new gen75_vebox_init_pipe_params() helper
function that initializes the filters mask and ensures the supplied
filters are going to be supported.

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
vebox: robustify frame store surface storage allocations.

Clean-up frame store surface storage allocation, rename the helper
function to gen75_vebox_ensure_surfaces_storage() and make it more
robust to allocation errors. i.e. propagate them up right away.

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>