Initial support for Broadcom VideoCore / BCM21553

This commit adds Broadcom support for:
* bionic/libc

Enable via:
* BOARD_USES_BROADCOM_HARDWARE := true
* COMMON_GLOBAL_CFLAGS += -DBCM_HARDWARE

Change-Id: Ia578f2dff7c2e2b2f15e9fdcfa55718bf0bd5bad