serial: 8250_early: Add earlycon for BCM2835 aux uart

Define the OF early console for BCM2835 aux UART, which can be enabled
by passing "earlycon" on the boot command line. This UART is found on
BCM283x and BCM27xx SoCs, a.k.a. Raspberry Pi in its variants.

Signed-off-by: Matthias Brugger <mbrugger@suse.com>
Link: https://lore.kernel.org/r/20200126123314.3558-1-matthias.bgg@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>