staging: brcm80211: removed last global function declaration in .c file

Code cleanup.
Signed-off-by: Roland Vossen <rvossen@broadcom.com>
Reviewed-by: Arend van Spriel <arend@broadcom.com>
Reviewed-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/brcm80211/brcmfmac/bcmsdh_sdmmc_linux.c

@@ -257,7 +257,6 @@ int brcmf_sdio_function_init(void)
 /*
  * module cleanup
 */
-extern int brcmf_sdio_remove(struct device *dev);
 void brcmf_sdio_function_cleanup(void)
 {
 	sd_trace(("%s Enter\n", __func__));