brcmsmac: remove set but not used variables 'phybw40, maxtargetpwr'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/wireless/broadcom/brcm80211/brcmsmac/phy/phy_lcn.c:1202:5: warning: variable 'phybw40' set but not used [-Wunused-but-set-variable]
drivers/net/wireless/broadcom/brcm80211/brcmsmac/phy/phy_lcn.c:4625:5: warning: variable 'phybw40' set but not used [-Wunused-but-set-variable]
drivers/net/wireless/broadcom/brcm80211/brcmsmac/phy/phy_lcn.c:4834:5: warning: variable 'phybw40' set but not used [-Wunused-but-set-variable]

drivers/net/wireless/broadcom/brcm80211/brcmsmac/phy/phy_lcn.c:3085:17: warning: variable 'maxtargetpwr' set but not used [-Wunused-but-set-variable]
drivers/net/wireless/broadcom/brcm80211/brcmsmac/phy/phy_lcn.c:4215:17: warning: variable 'maxtargetpwr' set but not used [-Wunused-but-set-variable]

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>