media: rockchip: rkcif: Add missing MUST_CONNECT flag to pads

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

media: rockchip: rkcif: Add missing MUST_CONNECT flag to pads

The pads missed checks for connected devices which may a null dereference

when the stream is enabled.

Unable to handle kernel NULL pointer dereference at virtual address

0000000000000020

pc : rkcif_interface_enable_streams+0x48/0xf0

lr : rkcif_interface_enable_streams+0x44/0xf0

Call trace:

rkcif_interface_enable_streams+0x48/0xf0

v4l2_subdev_enable_streams+0x26c/0x3f0

rkcif_stream_start_streaming+0x140/0x278

vb2_start_streaming+0x74/0x188

vb2_core_streamon+0xe0/0x1d8

vb2_ioctl_streamon+0x60/0xa8

v4l_streamon+0x2c/0x40

__video_do_ioctl+0x34c/0x400

video_usercopy+0x2d0/0x800

video_ioctl2+0x20/0x60

v4l2_ioctl+0x48/0x78