usb: gadget: Move requests init before the init of the functions

Due to the optimization for RNDIS/ECM functions, we need
to make sure that the requests together with its sps_params
are init before the init of the functions.
Otherwise the notify function might be called before requests
are init and incorrect values will be used.

Change-Id: I2019bbd3a5f2ee07b1337f75d3716e6f5def1110
Signed-off-by: Lena Salman <esalman@codeaurora.org>