This patch adds driver for Mini UART present in Raspberry Pi 3
and above, this UART is currently used as the primary UART in
these models.
The Mini UART is similar to ns16550, this driver is built
upon libchip/ns16550.
Use RTEMS_SYSINIT_ORDER_LAST_BUT_5 instead of RTEMS_SYSINIT_ORDER_LAST
to allow applications and support functions to place system
initialization handlers behind the standard handlers.
Update #3838.
