staging:rtl8192u: typedef struct tx_desc_819x_usb > struct tx_desc_819x_usb

Change structure tx_desc_819x_usb from being typedef to being a simple
structure, without the typedef.

checkpatch warns about defining new types in code.

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