drm/amdkfd: Save/restore vcc on gfx10

VCC moved out of user SGPR allocation in gfx10. It's now stored
in SGPRs 106-107.

Also fixes incorrect SGPR read offsets.

Cc: Shaoyun Liu <shaoyun.liu@amd.com>
Signed-off-by: Jay Cornwall <jay.cornwall@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: shaoyunl <shaoyun.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>