staging: rtl8723bs: Merge workaround conditionals into single else-if.

The if conditionals used to work around wrong TX power limit indices
can be condensed into a single if/else-if statement for more concise
expression.

Signed-off-by: Quytelda Kahja <quytelda@tamalin.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>