staging:rtl8192u: Rename function PHY_RF8256_Config() - Style

Rename the function PHY_RF8256_Config() to phy_rf8256_config(). This
change clears the checkpatch issue with CamelCase naming.

This is a simple coding style change which should have no impact on
runtime code execution.

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