usb: gadget: Initialize QTI control driver from rmnet function

QTI control driver is initialized as part of module_init. This
creates misc device upon boot up. Move the driver initialization
sequence to rmnet function driver initialization so that new QTI
control driver can create same misc device in its new function
driver initialization.

Change-Id: I627f4af0c9b3550c5e05b7e9d3f7873b37c069e0
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>