drm/amd/display: Add UHBR135 and UHBR20 into debugfs

Add support to manually force link rate to UHBR135 (0x546) and UHBR20
(0x7d0).
Tested-by: Mark Broadworth <mark.broadworth@amd.com>
Reviewed-by: Roman Li <Roman.Li@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Fangzhi Zuo <Jerry.Zuo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c

@@ -299,6 +299,8 @@ static ssize_t dp_link_settings_write(struct file *f, const char __user *buf,
 	case LINK_RATE_HIGH2:
 	case LINK_RATE_HIGH3:
 	case LINK_RATE_UHBR10:
+	case LINK_RATE_UHBR13_5:
+	case LINK_RATE_UHBR20:
 		break;
 	default:
 		valid_input = false;