drm/amdgpu: Add wrapper for freeing vbios memory

Use bios_release wrapper to release memory allocated for vbios image and
reset the variables.

v2:
	Use the same wrapper for clean up in sw_fini (Alex Deucher)

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>