accel/ivpu: Add fw_name file to debugfs

Add information about currently used firmware, makes test
automation of different firmware images easier.

Signed-off-by: Krystian Pradzynski <krystian.pradzynski@linux.intel.com>
Reviewed-by: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>
Signed-off-by: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230524074847.866711-6-stanislaw.gruszka@linux.intel.com