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