amdgpu: add the function to get the marketing name (v4)

This function is used to look up the marking name
for a specific board.

v2: agd: Squash in subsequent updates to the table.
v3: [Michel Dänzer]
* Make amdgpu_asic_id_table static, so it's not exported from
  libdrm_amdgpu.so.1
* Add amdgpu_get_marketing_name to amdgpu-symbols-check
* Fix indentation of second line of if statement
* Squash in another change removing redundant entries
* Change spelling of "RADEON" -> "Radeon"
* Remove "(TM)" from a minority of entries
v4: [Michel Dänzer]
* Use const char* instead of fixed size array for marketing_name (Emil
  Velikov)

Signed-off-by: Junwei Zhang <Jerry.Zhang@amd.com>
Reviewed-by: Flora Cui <Flora.Cui@amd.com>
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>