staging:rtl8192u: Remove SS_TH_low - Style

The member variable SS_TH_low is assigned a constant and then used
in a comparison. This member variable is redundant as the constant
can be used directly for the comparison.

In addition the constant RxPathSelection_SS_TH_low has been renamed
to RX_PATH_SELECTION_SS_TH_LOW, to clear the checkpatch issue with
CamelCase naming.

These changes are coding style in nature and should not impact
runtime code execution.

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