staging:rtl8192u: Remove typdef from enumeration RF90_RADIO_PATH_E - Style

Checkpatch warns about the creation of new types. This patch simply removes
the typedef from the enumeration RF90_RADIO_PATH_E to clear this checkpatch
warning. There should be no impact on run time code execution, as this is a
coding style issue only.

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