Fix /boot/ test in default environment.

If you've got everything on one partition, bootpath is set to "/boot/",
but the test in setargs was looking for "boot/", so it wound up using
the wrong root device.

Signed-off-by: Adam Sampson <ats@offog.org>
Update Sanei N90 settings to match a real board.

These were extracted from my M9701 (unbranded version of the N90) using
a10-meminfo-static. Total size is changed to 1GB, which matches ppizarro's
original description of his device, and on-die termination is enabled.

Signed-off-by: Adam Sampson <ats@offog.org>
Set io_width = 8 for the Sanei N90.

Oliver Schinagl suggested that this was a more appropriate setting for the
N90's DRAM configuration (4x Hynix H5TQ2G83CFR H9C 150HA).

Signed-off-by: Adam Sampson <ats@offog.org>