wiphy: add wiphy_get_allowed_freqs

This is more or less copied from scan_get_allowed_freqs but is
going to be needed by station (basically just saves the need for
station to do the same clone/constrain sequence itself).

One slight alteration is now a band mask can be passed in which
provides more flexibility for additional filtering.

src/wiphy.c

@@ -500,6 +500,21 @@ const struct scan_freq_set *wiphy_get_supported_freqs(
 	return wiphy->supported_freqs;
 }
 
+struct scan_freq_set *wiphy_get_allowed_freqs(const struct wiphy *wiphy,
+						uint32_t band_mask)
+{
+	struct scan_freq_set *allowed = scan_freq_set_clone(
+						wiphy->supported_freqs,
+						band_mask);
+
+	if (!wiphy_constrain_freq_set(wiphy, allowed)) {
+		scan_freq_set_free(allowed);
+		allowed = NULL;
+	}
+
+	return allowed;
+}
+
 static struct band *wiphy_get_band(const struct wiphy *wiphy, enum band_freq band)
 {
 	switch (band) {

src/wiphy.h

@@ -100,6 +100,8 @@ const char *wiphy_get_path(struct wiphy *wiphy);
 uint32_t wiphy_get_supported_bands(struct wiphy *wiphy);
 const struct scan_freq_set *wiphy_get_supported_freqs(
 						const struct wiphy *wiphy);
+struct scan_freq_set *wiphy_get_allowed_freqs(const struct wiphy *wiphy,
+						uint32_t band_mask);
 
 const struct band_freq_attrs *wiphy_get_frequency_info(
 						const struct wiphy *wiphy,