staging: rtl8192u: r8192U_core: fix missing struct leading to consistent spacing code style error

A missing struct keyword in variable declaration triggered a
need consistent spacing around '*' code style error. The struct
keyword thus has been added everywhere for the rtl8192_rx_info
struct, and therefore its typedef removed as not needed anymore.

Signed-off-by: Raphaël Beamonte <raphael.beamonte@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>