drm/amd/display: Remove inaccessible registers from DMU diagnostics

[Why]
SEC_CNTL isn't readable by x86 and can block Z8 entry if read.

[How]
Remove the read.

Reviewed-by: Ovidiu Bunea <ovidiu.bunea@amd.com>
Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Zaeem Mohamed <zaeem.mohamed@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dmub/src/dmub_dcn35.c

@@ -464,7 +464,7 @@ uint32_t dmub_dcn35_get_current_time(struct dmub_srv *dmub)
 
 void dmub_dcn35_get_diagnostic_data(struct dmub_srv *dmub, struct dmub_diagnostic_data *diag_data)
 {
-	uint32_t is_dmub_enabled, is_soft_reset, is_sec_reset;
+	uint32_t is_dmub_enabled, is_soft_reset;
 	uint32_t is_traceport_enabled, is_cw6_enabled;
 
 	if (!dmub || !diag_data)
@@ -514,9 +514,6 @@ void dmub_dcn35_get_diagnostic_data(struct dmub_srv *dmub, struct dmub_diagnosti
 	REG_GET(DMCUB_CNTL2, DMCUB_SOFT_RESET, &is_soft_reset);
 	diag_data->is_dmcub_soft_reset = is_soft_reset;
 
-	REG_GET(DMCUB_SEC_CNTL, DMCUB_SEC_RESET_STATUS, &is_sec_reset);
-	diag_data->is_dmcub_secure_reset = is_sec_reset;
-
 	REG_GET(DMCUB_CNTL, DMCUB_TRACEPORT_EN, &is_traceport_enabled);
 	diag_data->is_traceport_en  = is_traceport_enabled;