staging:rtl8192u: Rename RateAdaptiveTH_High - Style

The constant RateAdaptiveTH_High causes a checkpatch issue with respect
to CamelCase naming. As a result the constant has been renamed to
RATE_ADAPTIVE_TH_HIGH.

This 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>