drm/i915/gen9: Removed byte swapping for csr firmware

This patch contains the changes to remove the byte
swapping logic introduced with old dmc firmware.
While debugging PC10 entry issue for skylake found
with latest dmc firmware version 1.18 without byte
swapping dmc is working fine and able to enter PC10.

Note that apparently this was changed with dmc version 1.0 and earlier
ones indeed are byteswapped like this ...

v1: Initial version.

v2: Corrected firmware size during memcpy(). (Suggested by Sunil)

Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Damien Lespiau <damien.lespiau@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Sunil Kamath <sunil.kamath@intel.com>
Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Signed-off-by: Vathsala Nagaraju <vathsala.nagaraju@intel.com>
Reviewed-by: A.Sunil Kamath <sunil.kamath@intel.com>
[danvet: Add note that this only holds for released dmc firmware.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>