drm/amdgpu/bu: update mtype_local parameter settings

Update mtype_local module parameter to use MTYPE_RW by default.

0: MTYPE_RW (default)
1: MTYPE_NC
2: MTYPE_CC

Signed-off-by: Graham Sider <Graham.Sider@amd.com>
Reviewed-by: Harish Kasiviswanathan <Harish.Kasiviswanathan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>