Convert the documentation for the Broadcom BCM7445 and BCM7260 boards
to reStructuredText format and add the new filename to
doc/board/broadcom/index.rst.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

Remove ns16550 configuration from header files.  Document
DM_SERIAL-required prior stage device tree configuration.

Add support for loading U-Boot on the Broadcom 7445 SoC.  This port
assumes Broadcom's BOLT bootloader is acting as the second stage
bootloader, and U-Boot is acting as the third stage bootloader, loaded
as an ELF program by BOLT.

Signed-off-by: Thomas Fitzsimmons <fitzsim@fitzsim.org>
Cc: Stefan Roese <sr@denx.de>
Cc: Tom Rini <trini@konsulko.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>