staging:rtl8192u: Make function rtl8192_phyConfigBB static

The function rtl8192_phyConfigBB is only used in the file in which it
is defined so can be declared static. Additionally the prototype has
been removed from the header file, as it is not used.

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