drm/connector: hdmi: Fix memory leak in drm_display_mode_from_cea_vic()

drm/connector: hdmi: Fix memory leak in drm_display_mode_from_cea_vic()

modprobe drm_connector_test and then rmmod drm_connector_test,
the following memory leak occurs.

The `mode` allocated in drm_mode_duplicate() called by
drm_display_mode_from_cea_vic() is not freed, which cause the memory leak:

	unreferenced object 0xffffff80cb0ee400 (size 128):
	  comm "kunit_try_catch", pid 1948, jiffies 4294950339
	  hex dump (first 32 bytes):
	    14 44 02 00 80 07 d8 07 04 08 98 08 00 00 38 04  .D............8.
	    3c 04 41 04 65 04 00 00 05 00 00 00 00 00 00 00  <.A.e...........
	  backtrace (crc 90e9585c):
	    [<00000000ec42e3d7>] kmemleak_alloc+0x34/0x40
	    [<00000000d0ef055a>] __kmalloc_cache_noprof+0x26c/0x2f4
	    [<00000000c2062161>] drm_mode_duplicate+0x44/0x19c
	    [<00000000f96c74aa>] drm_display_mode_from_cea_vic+0x88/0x98
	    [<00000000d8f2c8b4>] 0xffffffdc982a4868
	    [<000000005d164dbc>] kunit_try_run_case+0x13c/0x3ac
	    [<000000006fb23398>] kunit_generic_run_threadfn_adapter+0x80/0xec
	    [<000000006ea56ca0>] kthread+0x2e8/0x374
	    [<000000000676063f>] ret_from_fork+0x10/0x20
	......

Free `mode` by using drm_kunit_display_mode_from_cea_vic()
to fix it.

Cc: stable@vger.kernel.org
Fixes: abb6f74973e2 ("drm/tests: Add HDMI TDMS character rate tests")
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241030023504.530425-3-ruanjinjie@huawei.com
Signed-off-by: Maxime Ripard <mripard@kernel.org>