drm/amdkfd: Add Arcturus GWS support and fix VG10

Add support for GWS in Arcturus, which needs MEC2 firmware #48
or above. Fix the MEC2 version check for Vega 10 GWS support,
since Vega 10 firmware adds 0x8000 to the actual firmware
revision. We were previously declaring support where it did not
exist.

Signed-off-by: Joseph Greathouse <Joseph.Greathouse@amd.com>
Reviewed-by: Kent Russell <kent.russell@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>