staging: rtl8723bs: Merge conditionals with similar bodies.

Two conditionals that set 'channel' based on 'band_type' in
'phy_get_tx_pwr_lmt()' can be simplified into one single-line conditional.

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