brcm80211: remove an unneeded NULL check

This code causes a static checker warning because "pi" gets dereferenced
before it is checked.  The dereference is inside the write_phy_reg()
function which is called from wlc_phy_write_txmacreg_nphy().

This code is only called from wlc_phy_init_nphy() and "pi" is a
valid pointer so we can remove the check for NULL.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/brcm80211/brcmsmac/phy/phy_n.c

@@ -14358,7 +14358,7 @@ void wlc_phy_nphy_tkip_rifs_war(struct brcms_phy *pi, u8 rifs)
 
 	wlc_phy_write_txmacreg_nphy(pi, holdoff, delay);
 
-	if (pi && pi->sh && (pi->sh->_rifs_phy != rifs))
+	if (pi->sh && (pi->sh->_rifs_phy != rifs))
 		pi->sh->_rifs_phy = rifs;
 }