drm/i915/guc: Request RP0 before loading firmware

By default, GT (and GuC) run at RPn. Requesting for RP0
before firmware load can speed up DMA and HuC auth as well.
In addition to writing to 0xA008, we also need to enable
swreq in 0xA024 so that Punit will pay heed to our request.

SLPC will restore the frequency back to RPn after initialization,
but we need to manually do that for the non-SLPC path.

We don't need a manual override in the SLPC disabled case, just
use the intel_rps_set function to ensure consistent RPS state.

Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Reviewed-by: Sujaritha Sundaresan <sujaritha.sundaresan@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211216233022.21351-1-vinay.belgaumkar@intel.com