drm/amdgpu: handle more than 10 UVD sessions (v2)

Change History
--------------

v2:
- Make firmware version check correctly. Firmware
  versions >= 1.80 should all support 40 UVD
  instances.
- Replace AMDGPU_MAX_UVD_HANDLES with max_handles
  variable.

v1:
- The firmware can handle upto 40 UVD sessions.

Signed-off-by: Arindam Nath <arindam.nath@amd.com>
Signed-off-by: Ayyappa Chandolu <ayyappa.chandolu@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>