ARM: start kernel: find a valid address for the atags list automatically
If a board does not specify a place for the atags list default to
SDRAM start + 0x100. The vast majority of boards uses this place
anyway, so the call to armlinux_set_bootparams() can be removed
for most boards.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>