[M] Change in flashrom[main]: ichspi: Add support for C740 PCH

[David Hendricks (Code Review)]

Attention is currently required from: Anastasia Klimchuk, Kyösti Mälkki, Patrick Georgi, Patrick Rudolph.

David Hendricks has posted comments on this change. ( https://review.coreboot.org/c/flashrom/+/78186?usp=email )

Change subject: ichspi: Add support for C740 PCH
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Patch Set 4:

(1 comment)

File ich_descriptors.c:

https://review.coreboot.org/c/flashrom/+/78186/comment/49ca7976_35ea16fb :
PS4, Line 1039: 			return CHIPSET_C740_SERIES_EMMITSBURG;
For Lewisburg the ISL value should be 0x8b (139) (see also: CB:57581). That matches the value seen when running `ifdtool -d` on the latest (2023.3 IPU) BKC images as well as the PCH strap length value mentioned in the C620 SPI PG (doc #559021).

Not sure if it's better to fix it here or in another patch. Also, there was some discussion a while ago as to whether we should use `==` or `<=` for these comparisons, and IIRC the consensus at the time was to use '<=`.

Anyway, the change you've made here for EBG looks fine, but we should probably correct the LBG value rather than removing it.