staging:rtl8192u: Rename RTL819xU_MODULE_NAME - Style

Rename the MACRO RTL819xU_MODULE_NAME to RTL819XU_MODULE_NAME, this
clears the checkpatch issue with CamelCase naming.

This is 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>