brcmfmac: add dedicated USB log level.

Add USB log level and update and add log messages in usb module.
Reviewed-by: Arend Van Spriel <arend@broadcom.com>
Signed-off-by: Hante Meuleman <meuleman@broadcom.com>
Signed-off-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/brcm80211/brcmfmac/dhd_dbg.h

@@ -31,6 +31,7 @@
 #define BRCMF_EVENT_VAL	0x0400
 #define BRCMF_BTA_VAL	0x0800
 #define BRCMF_FIL_VAL	0x1000
+#define BRCMF_USB_VAL	0x2000
 
 #if defined(DEBUG)