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