drm/amdgpu: Add nbio 7.4 support for vega20 (v3)

Some register offset in nbio v7.4 are different with v7.0.
We need a seperate nbio_v7_4.c for vega20.

v2: fix doorbell range for sdma (Alex)
v3: squash in static fix (kbuild test robot)

Signed-off-by: Feifei Xu <Feifei.Xu@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/Makefile

@@ -62,7 +62,7 @@ amdgpu-$(CONFIG_DRM_AMDGPU_SI)+= si.o gmc_v6_0.o gfx_v6_0.o si_ih.o si_dma.o dce
 
 amdgpu-y += \
 	vi.o mxgpu_vi.o nbio_v6_1.o soc15.o emu_soc.o mxgpu_ai.o nbio_v7_0.o vega10_reg_init.o \
-	vega20_reg_init.o
+	vega20_reg_init.o nbio_v7_4.o
 
 # add DF block
 amdgpu-y += \