drm/amd: Add SDMA functions to kfd-->kgd interface

This patch adds three new functions to the kfd2kgd interface:

- hqd_sdma_load() - Loads SDMA mqd to a H/W SDMA hqd slot. Used only in no HWS
                    mode.

- hqd_sdma_is_occupied() - Checks if an SDMA hqd slot is occupied. Used only
                           in no HWS mode.

- hqd_sdma_destroy() - Destructs and preempts the SDMA queue assigned to
                       that SDMA hqd slot. Used only in no HWS mode.

These functions are needed to support SDMA queues scheduling when using no HWS
mode (used for debug or bring-up).

v2: Removed init_sdma_engines() from interface. Initialization is done in
radeon.

Signed-off-by: Ben Goz <ben.goz@amd.com>
Signed-off-by: Oded Gabbay <oded.gabbay@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>