staging/rtl8187se: Remove temporary variable for return value

The simple PlatformIORead1Byte function doesn't need to store its return
value in a temporary variable; rather simply return the value directly.

By moving the function to the top we can also get rid of the forward
declaration.

The wrapper functions could be easily replaced by direct calls to
read_nic_byte but is kept for readability.

Since this functions is local only we can mark it as static.

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