Change in flashrom[master]: Add initial J-Link SPI programmer

[Nico Huber (Code Review)]

Nico Huber has posted comments on this change. ( https://review.coreboot.org/28087 )

Change subject: Add initial J-Link SPI programmer
......................................................................

Patch Set 1:

(1 comment)

https://review.coreboot.org/#/c/28087/1/jlink_spi.c
File jlink_spi.c:

https://review.coreboot.org/#/c/28087/1/jlink_spi.c@168
PS1, Line 168: 	.max_data_read	= JTAG_MAX_TRANSFER_SIZE,
The correct interpretation of the comment above is that
we have to tell here how much payload we can take. Which
is `JTAG_MAX_TRANSFER_SIZE - 4` or `- 5` if we allow 4B
addresses. (The interface is just wrong and should change
in the future. The SPI drivers shouldn't predict the
protocol overhead. But for now we have to do the calcu-
lation here.)

Please add `- 5` to both `.max_data_(read|write)`, and
set `.features = SPI_MASTER_4BA,` (I don't see a reason
why it shouldn't work oob).