usb: gadget: qti: Add compat_ioctl

The .compat_ioctl callback will be called if 32-bit userspace
issues an ioctl to a 64-bit kernel. Currently the supported
IOCTLs have matching signatures between 32- and 64-bit, so
simply use the existing rmnet_ctrl_ioctl function.

Change-Id: Ic2176c011dcd34485c0dad542e68745802beb182
Signed-off-by: Jack Pham <jackp@codeaurora.org>