amdgpu: add firmware for vega12

From 18.40 release.

From internal git commit:
27b92ecf906ad48e017221fe062d5ab189f0d9dd

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Josh Boyer <jwboyer@kernel.org>

WHENCE

@@ -2160,6 +2160,20 @@ File: amdgpu/vega10_smc.bin
 File: amdgpu/vega10_sos.bin
 File: amdgpu/vega10_uvd.bin
 File: amdgpu/vega10_vce.bin
+File: amdgpu/vega12_asd.bin
+File: amdgpu/vega12_ce.bin
+File: amdgpu/vega12_gpu_info.bin
+File: amdgpu/vega12_me.bin
+File: amdgpu/vega12_mec.bin
+File: amdgpu/vega12_mec2.bin
+File: amdgpu/vega12_pfp.bin
+File: amdgpu/vega12_rlc.bin
+File: amdgpu/vega12_sdma.bin
+File: amdgpu/vega12_sdma1.bin
+File: amdgpu/vega12_smc.bin
+File: amdgpu/vega12_sos.bin
+File: amdgpu/vega12_uvd.bin
+File: amdgpu/vega12_vce.bin
 File: amdgpu/raven_asd.bin
 File: amdgpu/raven_ce.bin
 File: amdgpu/raven_gpu_info.bin