staging:rtl8192u: Rename EEPROM_Default_PwDiff - Style

Rename the constant EEPROM_Default_PwDiff to EEPROM_DEFAULT_PW_DIFF,
this clears the checkpatch issue with CamelCase naming.

This change is purely a 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>