qcacmn: Add wbuff include path for spectral compilation

wbuff is a module which maintains a pre-allocated pool of
skbs for each registered module and allocates skbs when
requested. Add wbuff/inc in include path for qca_spectral
compilation.

Change-Id: I6bc9eaca99f7789eaa5cb0500d0258495caf7ea4
CRs-Fixed: 2313935

spectral/Kbuild

@@ -28,6 +28,7 @@ INCS += -I$(obj)/$(DEPTH)/cmn_dev/os_if/linux/spectral/inc
 INCS += -I$(obj)/$(DEPTH)/cmn_dev/os_if/linux/scan/inc
 INCS += -I$(obj)/$(DEPTH)/cmn_dev/spectral/core
 INCS += -I$(obj)/$(DEPTH)/cmn_dev/target_if/direct_buf_rx/inc
+INCS += -I$(obj)/$(DEPTH)/cmn_dev/wbuff/inc
 
 ifeq ($(WLAN_CONV_CRYPTO_SUPPORTED), 1)
 INCS += -I$(obj)/$(DEPTH)/cmn_dev/umac/cmn_services/crypto/inc