brcm80211: smac: remove redundant assignments from txpwrctrl_pwr_setup_nphy

The function wlc_phy_txpwrctrl_pwr_setup_nphy() does assign a local
variable target_pwr_qtrdbm in several code paths, but in the end all
code paths are coming to an assignment of that variable which does
override all previous. So those early and redundant assignments have
been removed.

Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Alwin Beukers <alwin@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>