[media] v4l2-ctrl: Suppress build warning from v4l2_ctrl_new_std_menu()

Prevent following build warning:
drivers/media/v4l2-core/v4l2-ctrls.c: In function v4l2_ctrl_new_std_menu:
drivers/media/v4l2-core/v4l2-ctrls.c:1768:15: warning: 'qmenu_int_len' may be used uninitialized in this function

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Cc: Arun Kumar K <arun.kk@samsung.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>