drm/amdgpu: Switch error code when bo pin fails. (v3)

Switching to -ENOMEM resolves a hang in case the driver
uses this function in atomic code path.

v2: Update commit message.
v3:
Remove forcing -EINVAL in case of amdgpu_bo_pin fail
since there is no apparent reason for not just passing
through the the return value.

Signed-off-by: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_display.c

@@ -189,7 +189,6 @@ int amdgpu_crtc_page_flip_target(struct drm_crtc *crtc,
 
 	r = amdgpu_bo_pin(new_abo, AMDGPU_GEM_DOMAIN_VRAM, &base);
 	if (unlikely(r != 0)) {
-		r = -EINVAL;
 		DRM_ERROR("failed to pin new abo buffer before flip\n");
 		goto unreserve;
 	}