staging: rtl8712: usb_ops.c: Remove leading p from variable names

Remove leading 'p' from the names of the following pointer variables:
- pintfhdl
- pintf_hdl (renamed to intfhdl in keeping with the convention in other
functions)
- poption
- pops
- pintfpriv.
Issue found with Coccinelle.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>