media: renesas-ceu: fix compiler warning

In function 'strncpy',
    inlined from 'ceu_notify_complete' at drivers/media/platform/renesas-ceu.c:1378:2:
include/linux/string.h:246:9: warning: '__builtin_strncpy' output truncated before terminating nul copying 11 bytes from a string of the same length [-Wstringop-truncation]
  return __builtin_strncpy(p, q, size);
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Cc: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>