staging: rtl8723bs: Add missing curly braces on else statement.

Fix 'braces {} should be used on all arms of this statement' coding
style problem in 'phy_get_tx_pwr_lmt()'.

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