ARM: dts: rainier: Add reserved memory for ramoops

Reserve a 1.5MiB region of memory to record kmsg dumps, console and
userspace message state into 16kiB ring-buffer slots. The sizing allows
for up to 16 dumps to be captured and read out.

Set max-reason to KMSG_DUMP_EMERG to capture bad-path reboots.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20201022014731.2035438-6-andrew@aj.id.au


Signed-off-by: Joel Stanley <joel@jms.id.au>