Fix memory leak in drm_display_mode_from_cea_vic()

Summary

In the Linux kernel, the following vulnerability has been resolved: 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.