qcacmn: Check whether Spectral is disabled upon setting rxchainmask

When Spectral is disabled via INI and the rxchainmask is set for
the radio via iwpriv/cfg80211tool, it results in null pointer access
of target_if_spectral pointer. To fix this, add Spectral feature check
inside target_if_spectral_set_rxchainmask.

Change-Id: Ibd43d3bbc8622d4b8502653b55511bb4667cec7a
CRs-Fixed: 2380653

spectral/dispatcher/src/wlan_spectral_utils_api.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2018 The Linux Foundation. All rights reserved.
+ * Copyright (c) 2017-2019 The Linux Foundation. All rights reserved.
  *
  *
  * Permission to use, copy, modify, and/or distribute this software for
@@ -182,6 +182,8 @@ wlan_lmac_if_sptrl_register_rx_ops(struct wlan_lmac_if_rx_ops *rx_ops)
 	sptrl_rx_ops->sptrlro_vdev_get_ch_width = spectral_vdev_get_ch_width;
 	sptrl_rx_ops->sptrlro_vdev_get_sec20chan_freq_mhz =
 	    spectral_vdev_get_sec20chan_freq_mhz;
+	sptrl_rx_ops->sptrlro_spectral_is_feature_disabled =
+		wlan_spectral_is_feature_disabled;
 }
 
 void