ichspi: Fix number of bytes for HW seq operations

This patch fixes a potential issue where the SPI controller register
HSFC.FDBC (bits 24-29) value gets incorrectly calculated while passing
the `len` as `0` instead of `1`.

As per Intel EDS, `0b` in the FDBC represents 1 byte while `0x3f`
represents 64-bytes to be transferred. The number of bytes
transferred is the value of this field plus 1.

If we would like to transfer 1 byte then we need to set `0b` in
FDBC for operations like read, write, flash id as to account for
the `set byte count` hence, the `len` argument should be `1`.

Additionally, as per EDS, the FDBC field is ignored for any block
erase command.

BUG=b:258280679
TEST=Able to build flashrom and perform below operations on Google,
Rex and Google, Kano/Taeko.

During `--wp-disable` HW seq operation that requires 1 byte data
transfer.

HSFC.FDBC value while passing `len` as `0` = 0x3f (represents 64-byte)

HSFC.FDBC value while passing `len` as `1` = 0x0 (represents 1-byte)

Original-Signed-off-by: Subrata Banik <subratabanik@google.com>
Original-Change-Id: I5b911655649c693e576497520687d7810bbd3c54
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/69789
Original-Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Original-Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Original-Reviewed-by: Nikolai Artemiev <nartemiev@google.com>
Original-Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

Change-Id: Id54cb06bc66e86f95ea652ee604715e8969bcb02
Signed-off-by: Felix Singer <felixsinger@posteo.net>
---
M ichspi.c
1 file changed, 53 insertions(+), 3 deletions(-)