staging: brcm80211: move header file

Move the pci_core.h header file from util to include subdir, in preparation for
other moves and cleanup.

Cc: devel@linuxdriverproject.org
Cc: linux-wireless@vger.kernel.org
Reviewed-by: Brett Rudley <brudley@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>