drm/amd/display: make variables static

As "dcn3_1_soc", "dcn3_15_soc", and "dcn3_16_soc" are not used outside
of their corresponding "dcn3*_fpu.c", make them static and remove their
extern declaration.

Fixes: 26f4712a ("drm/amd/display: move FPU related code from dcn31 to dml/dcn31 folder")
Fixes: fa896297 ("drm/amd/display: move FPU related code from dcn315 to dml/dcn31 folder")
Fixes: 3f8951cc ("drm/amd/display: move FPU related code from dcn316 to dml/dcn31 folder")
Signed-off-by: Magali Lemes <magalilemes00@gmail.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Reviewed-by: Maíra Canal <mairacanal@riseup.net>
Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn31/dcn31_resource.h

@@ -32,7 +32,6 @@
 	container_of(pool, struct dcn31_resource_pool, base)
 
 extern struct _vcs_dpi_ip_params_st dcn3_1_ip;
-extern struct _vcs_dpi_soc_bounding_box_st dcn3_1_soc;
 
 struct dcn31_resource_pool {
 	struct resource_pool base;

drivers/gpu/drm/amd/display/dc/dcn315/dcn315_resource.h

@@ -32,7 +32,6 @@
 	container_of(pool, struct dcn315_resource_pool, base)
 
 extern struct _vcs_dpi_ip_params_st dcn3_15_ip;
-extern struct _vcs_dpi_ip_params_st dcn3_15_soc;
 
 struct dcn315_resource_pool {
 	struct resource_pool base;

drivers/gpu/drm/amd/display/dc/dcn316/dcn316_resource.h

@@ -32,7 +32,6 @@
 	container_of(pool, struct dcn316_resource_pool, base)
 
 extern struct _vcs_dpi_ip_params_st dcn3_16_ip;
-extern struct _vcs_dpi_ip_params_st dcn3_16_soc;
 
 struct dcn316_resource_pool {
 	struct resource_pool base;

drivers/gpu/drm/amd/display/dc/dml/dcn31/dcn31_fpu.c

@@ -114,7 +114,7 @@ struct _vcs_dpi_ip_params_st dcn3_1_ip = {
 	.dcc_supported = true,
 };
 
-struct _vcs_dpi_soc_bounding_box_st dcn3_1_soc = {
+static struct _vcs_dpi_soc_bounding_box_st dcn3_1_soc = {
 		/*TODO: correct dispclk/dppclk voltage level determination*/
 	.clock_limits = {
 		{
@@ -259,7 +259,7 @@ struct _vcs_dpi_ip_params_st dcn3_15_ip = {
 	.dcc_supported = true,
 };
 
-struct _vcs_dpi_soc_bounding_box_st dcn3_15_soc = {
+static struct _vcs_dpi_soc_bounding_box_st dcn3_15_soc = {
 	.sr_exit_time_us = 9.0,
 	.sr_enter_plus_exit_time_us = 11.0,
 	.sr_exit_z8_time_us = 50.0,
@@ -355,7 +355,7 @@ struct _vcs_dpi_ip_params_st dcn3_16_ip = {
 	.dcc_supported = true,
 };
 
-struct _vcs_dpi_soc_bounding_box_st dcn3_16_soc = {
+static struct _vcs_dpi_soc_bounding_box_st dcn3_16_soc = {
 		/*TODO: correct dispclk/dppclk voltage level determination*/
 	.clock_limits = {
 		{