XO-1.75 change machine signature for firmware

[Quozl]

We used CL1 as the machine signature in the .rom file for XO-1 and XO-1.5, so for XO-1.75 we will use CL2.

svn 2120 contains the first half of the change, such that the next release of the firmware will refuse CL1 .rom files unless the downgrade word is used first.

After next release, we are to change olpc.bth to use CL2 for the following release.

[Quozl]

svn 2148 contains the second half of the change.

[Quozl]

svn 2148 broke flash on Q4A11 and Q4A12. crc-offset is already different on each machine, and this prevents accidental install. Removed the CL1 vs CL2 check in svn 2153.

[Quozl]

A new requirement has emerged that the firmware machine signature should read CL3.

[Quozl]

svn 2158 adds machine signature check again.

OLPC D1, 1 GiB memory installed, 4 GB internal storage, S/N SHC93701192
OpenFirmware  Q3A62q   EC Firmware Ver:2.0.1

ok flash u:\q4a13.rom       
Reading u:\q4a13.rom
Got firmware version: CL2   Q4A13  Q4A
Wrong machine signature
ok 

OpenFirmware machine signature strings and laptop models:

CL1	XO-1	(AMD Geode laptop)
CL1	XO-1.5	(VIA C7 laptop)
CL2	XO-1.75	(ARM laptop)
CL3	XO-3	(ARM tablet)

Expected outcome of flashing firmware on hardware:

On hardware:	XO-1	XO-1.5	XO-1.75	XO-3
Flashing XO-1 firmware	ok	crc	ms	ms
Flashing XO-1.5 firmware	crc	ok	ms	ms
Flashing XO-1.75 firmware	crc	crc	ok	ms
Flashing XO-3 firmware	crc	crc	ms	ok

• ok - success,
• crc - Firmware image has bad internal CRC, (except where XO-1 and XO-1.5 firmware updates beyond svn 2158),
• ms - Wrong machine signature.

[Quozl]

svn 2159 changes machine signature check to use a value defined in dictionary during build, since SPI FLASH is not memory mapped on XO-1.75.

[Quozl]

XO-1.5 aspect of this ticket is completed, in Q3A63.

[Quozl]

XO-1.75 aspect of this ticket is completed, in Q4A14.