drm:amd:amdgpu: Fix missing buffer object unlock in failure path

smatch warning -
1) drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:3615 gfx_v9_0_kiq_resume()
warn: inconsistent returns 'ring->mqd_obj->tbo.base.resv'.

2) drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c:6901 gfx_v10_0_kiq_resume()
warn: inconsistent returns 'ring->mqd_obj->tbo.base.resv'.

Signed-off-by: Sukrut Bellary <sukrut.bellary@linux.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>