staging/rtl8187se: Reuse ReadBBPortUchar to avoid duplicated code

WriteBBPortUchar reimplements ReadBBPortUchar in its body, so we can
remove the duplicated code by calling ReadBBPortUchar directly.

Unfortunately we have to move ReadBBPortUchar around; while at it we can
also get rid of the temporary variable for the return value.

Also we can remove the local variables UCharData and RegisterContent in
WriteBBPortUchar as they are not used / without effect.

Both functions are only 'local' so we can mark them as static.

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>