drm/amdgpu: Use new drm_fb_helper functions
drm/amdgpu: Use new drm_fb_helper functions

Use the newly created wrapper drm_fb_helper functions instead of calling
core fbdev functions directly. They also simplify the fb_info creation.

v3:
- Don't touch remove_conflicting_framebuffers

v2:
- Fixed PTR_ERR issue mentioned by kbuild bot

Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Oded Gabbay <oded.gabbay@gmail.com>
Cc: "Christian König" <christian.koenig@amd.com>

Signed-off-by: Archit Taneja <c3c1a2580afd741e2758c6f57ef6c9e85c629c83@codeaurora.org>
Signed-off-by: Daniel Vetter <c1b6782c4af8f0673da8923a0702a1832e5940f4@ffwll.ch>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs