This commit add a very basic code to allow Barebox to be booted from
IRAM. Given that the amount of IRAM on most i.MX variants is
insufficient to contain a copy of Barebox with any reasonable degree
of functionality this code uses IRAM only as a temporary location and
eventually bootstraps from DRAM. But the presense of the intermediate
IRAM-only stage allows to add provisions to test the area of DRAM that
Barebox would be using to facilitate various testing scenarious.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>