usb: net: sierra: check for no status endpoint

usb: net: sierra: check for no status endpoint

The driver checks for having three endpoints and
having bulk in and out endpoints, but not that
the third endpoint is interrupt input.
Rectify the omission.

Reported-by: syzbot+3f89ec3d1d0842e95d50@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-usb/686d5a9f.050a0220.1ffab7.0017.GAE@google.com/
Tested-by: syzbot+3f89ec3d1d0842e95d50@syzkaller.appspotmail.com
Fixes: eb4fd8cd355c8 ("net/usb: add sierra_net.c driver")
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Link: https://patch.msgid.link/20250714111326.258378-1-oneukum@suse.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>