drm/amd/display: Add ASICREV_IS_PICASSO

[WHY]
We only want to load DMCU FW on Picasso and Raven 2, not on Raven 1.

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org