drm/i915/tc: Fix -Wformat-truncation in intel_tc_port_init

Fix below compiler warning:

intel_tc.c:1879:11: error: ‘%d’ directive output may be truncated
writing between 1 and 11 bytes into a region of size 3
[-Werror=format-truncation=]
"%c/TC#%d", port_name(port), tc_port + 1);
           ^~
intel_tc.c:1878:2: note: ‘snprintf’ output between 7 and 17 bytes
into a destination of size 8
  snprintf(tc->port_name, sizeof(tc->port_name),
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    "%c/TC#%d", port_name(port), tc_port + 1);
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

v2: use kasprintf(Imre)
v3: use const for port_name, and fix tc mem leak(Imre)

Fixes: 3eafcddf ("drm/i915/tc: Move TC port fields to a new intel_tc_port struct")
Cc: Mika Kahola <mika.kahola@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231026125636.5080-1-nirmoy.das@intel.com

drivers/gpu/drm/i915/display/intel_tc.c

@@ -58,7 +58,7 @@ struct intel_tc_port {
 	struct delayed_work link_reset_work;
 	int link_refcount;
 	bool legacy_port:1;
-	char port_name[8];
+	const char *port_name;
 	enum tc_port_mode mode;
 	enum tc_port_mode init_mode;
 	enum phy_fia phy_fia;
@@ -1875,8 +1875,12 @@ int intel_tc_port_init(struct intel_digital_port *dig_port, bool is_legacy)
 	else
 		tc->phy_ops = &icl_tc_phy_ops;
 
-	snprintf(tc->port_name, sizeof(tc->port_name),
-		 "%c/TC#%d", port_name(port), tc_port + 1);
+	tc->port_name = kasprintf(GFP_KERNEL, "%c/TC#%d", port_name(port),
+				  tc_port + 1);
+	if (!tc->port_name) {
+		kfree(tc);
+		return -ENOMEM;
+	}
 
 	mutex_init(&tc->lock);
 	/* TODO: Combine the two works */
@@ -1897,6 +1901,7 @@ void intel_tc_port_cleanup(struct intel_digital_port *dig_port)
 {
 	intel_tc_port_suspend(dig_port);
 
+	kfree(dig_port->tc->port_name);
 	kfree(dig_port->tc);
 	dig_port->tc = NULL;
 }