add new registers: mmCGTT_SPI_CLK_CTRL, mmDB_DEBUG3 and
mmGL2C_CGTT_SCLK_CTRL.
Reviewed-by: NJack Xiao <Jack.Xiao@amd.com>
Signed-off-by: NTianci Yin <tianci.yin@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>