staging:rtl8192u: Remove typedef from structure - Style

Remove the typedef directive from struct _CHNL_TXPOWER_TRIPLE. This is a
coding style change which clears a checkpatch issue with declaring new types.
There should be no impact on runtime execution.

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