Patch for flashrom r3254 / Autoskip feature for 82802ab-type chips

[Claus Gindhart]

Flash pages, which where excluded from updating using the exclude or the
layout option, as well as areas, whose flash contents already contain the
desired data, will be skipped.
These ensures absolute data security of critical areas (BIOS boot block), 
e.g. against a sudden power off or a CPU hangup during flashing. As a
nice side effect, it speeds up the flash process, if the BIOS to be flashed
is very similar to the version in flash.

Signed-off-by: Claus Gindhart

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Some remarks:
I need this feature urgently, because data retention of the BIOS boot block 
(and also some other data in some applications) is a mandatory requirement 
for me.
This patch only adds this feature for the 82802ab type flashes.
I will add this feature to all flash modules of the flash devices, we are 
using in our company; i have already running an improved jedec.c here, and 
will provide this patch soon. Some SPI devices will follow in some weeks.

[Stefan Reinauer]

Claus Gindhart wrote:
> Flash pages, which where excluded from updating using the exclude or the
> layout option, as well as areas, whose flash contents already contain the
> desired data, will be skipped.
> These ensures absolute data security of critical areas (BIOS boot block), 
> e.g. against a sudden power off or a CPU hangup during flashing. As a
> nice side effect, it speeds up the flash process, if the BIOS to be flashed
> is very similar to the version in flash.
>
> Signed-off-by: Claus Gindhart

Thanks! Committed in r3260

Stefan