drm/amdgpu: amdgpu{_reset}.h: fix all kernel-doc warnings

drm/amdgpu: amdgpu{_reset}.h: fix all kernel-doc warnings

Fix all kernel-doc warnings in amdgpu.h and amdgpu_reset.h:
- Use the struct keyword for kernel-doc struct comments.
- Use the correct enum names in enum amd_reset_method.

This eliminates these warnings:

Warning: drivers/gpu/drm/amd/amdgpu/amdgpu.h:477 cannot understand
 function prototype: 'struct amdgpu_wb'
Warning: drivers/gpu/drm/amd/amdgpu/amdgpu.h:576 Enum value
 'AMD_RESET_METHOD_LEGACY' not described in enum 'amd_reset_method'
Warning: drivers/gpu/drm/amd/amdgpu/amdgpu.h:576 Enum value
 'AMD_RESET_METHOD_MODE0' not described in enum 'amd_reset_method'
Warning: drivers/gpu/drm/amd/amdgpu/amdgpu.h:576 Enum value
 'AMD_RESET_METHOD_MODE1' not described in enum 'amd_reset_method'
Warning: drivers/gpu/drm/amd/amdgpu/amdgpu.h:576 Enum value
 'AMD_RESET_METHOD_MODE2' not described in enum 'amd_reset_method'
Warning: drivers/gpu/drm/amd/amdgpu/amdgpu.h:576 Enum value
 'AMD_RESET_METHOD_LINK' not described in enum 'amd_reset_method'
Warning: drivers/gpu/drm/amd/amdgpu/amdgpu.h:576 Enum value
 'AMD_RESET_METHOD_BACO' not described in enum 'amd_reset_method'
Warning: drivers/gpu/drm/amd/amdgpu/amdgpu.h:576 Enum value
 'AMD_RESET_METHOD_PCI' not described in enum 'amd_reset_method'
Warning: drivers/gpu/drm/amd/amdgpu/amdgpu.h:576 Enum value
 'AMD_RESET_METHOD_ON_INIT' not described in enum 'amd_reset_method'
Warning: drivers/gpu/drm/amd/amdgpu/amdgpu.h:576 Excess enum value
 '@AMD_RESET_LEGACY' description in 'amd_reset_method'
Warning: drivers/gpu/drm/amd/amdgpu/amdgpu.h:576 Excess enum value
 '@AMD_RESET_MODE0' description in 'amd_reset_method'
Warning: drivers/gpu/drm/amd/amdgpu/amdgpu.h:576 Excess enum value
 '@AMD_RESET_MODE1' description in 'amd_reset_method'
Warning: drivers/gpu/drm/amd/amdgpu/amdgpu.h:576 Excess enum value
 '@AMD_RESET_MODE2' description in 'amd_reset_method'
Warning: drivers/gpu/drm/amd/amdgpu/amdgpu.h:576 Excess enum value
 '@AMD_RESET_LINK' description in 'amd_reset_method'
Warning: drivers/gpu/drm/amd/amdgpu/amdgpu.h:576 Excess enum value
 '@AMD_RESET_BACO' description in 'amd_reset_method'
Warning: drivers/gpu/drm/amd/amdgpu/amdgpu.h:576 Excess enum value
 '@AMD_RESET_PCI' description in 'amd_reset_method'

Also move the enum to amdgpu_reset.h and eventually only forward declare
it in amdgpu.h. (Christian)

Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>