bwn(4): BWN_GPL_PHY: make compile again

compiler complains about error: comparison of different enumeration types
('bwn_phy_band_t' and 'bwn_band_t');  so use the correct enum value.

Sponsored by:	The FreeBSD Foundation
PR:		287695
Reported by:	(tom.mcclean gmail.com)
MFC after:	3 days

sys/gnu/dev/bwn/phy_n/if_bwn_phy_n_ppr.c

@@ -247,7 +247,7 @@ bool bwn_ppr_load_max_from_sprom(struct bwn_mac *mac, struct bwn_ppr *ppr,
 		}
 	}
 
-	if (band == BWN_BAND_2G) {
+	if (band == BWN_PHY_BAND_2G) {
 		uint16_t ck2gpo;
 
 		error = bhnd_nvram_getvar_uint16(sc->sc_dev, BHND_NVAR_CCK2GPO,