SPL is now designed so core X1000 code is in control of the boot,
under the reasonable assumption that the device boots from flash.
It should not be too hard to adapt to other X1000 ports.
The biggest functional change is that the SPL can now read/write
the flash, under the control of a host computer. The SPL relies
on the boot ROM for USB communication, so the host has to execute
the SPL multiple times following a protocol.
Change-Id: I3ffaa00e4bf191e043c9df0e2e64d15193ff42c9
