staging: rtl8188eu: Instead of intf_hdl pass adapter in read & write functions

intf_hdl is passed in usb_[read,write][8,16,32]() functions, which
is then passed to vender_request() there it's used to get adapter pointer,
so instead of passing intf_hdl we can directly pass adapter.

This change will also help in removing rtw_[read,write][8,16,32]() wrapper
functions being used to call usb_[read,write][8,16,32]() functions.

Signed-off-by: navin patidar <navin.patidar@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>