staging:rtl8192u: typedef struct rx_desc_819x_usb remove typedef

Change structure rx_desc_819x_usb from being typedef to being a simple
structure, without the typedef.

Clears a checkpatch issue, definging new types in the code.

Signed-off-by: John Whitmore <johnfwhitmore@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>