[ARM] 5535/1: U300 Makefile.boot

The Makefile.boot file for the U300 port. This will compile the
kernel for different ZRELADDR depending on the location of
physical RAM in the chosen configuration.

Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>