Change in flashrom[master]: bitbang-spi.c: support clock polarity and phase

[Xiang W (Code Review)]

Attention is currently required from: Xiang W, Edward O'Callaghan, Angel Pons.
Hello build bot (Jenkins), Stefan Reinauer, Edward O'Callaghan, Angel Pons, Anastasia Klimchuk,

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/flashrom/+/49255

to look at the new patch set (#27).

Change subject: bitbang-spi.c: support clock polarity and phase
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bitbang-spi.c: support clock polarity and phase

SPI has four modes, which are determined by Clock polarity and Clock
phase. See https://en.wikipedia.org/wiki/Serial_Peripheral_Interface#Clock_polarity_and...
for details. The previous code only supports one mode and may not be
able to handle some special spi flash. This patch uses spi's mode0 by
default to be consistent with the previous code.

TEST=build and run flashrom with sysfsgpio on raspberrypi to read  W25Q128.V

Change-Id: I04c1dfe132d756119229b27c3cd611d1be1abc8d
Signed-off-by: Xiang Wang 
---
M bitbang_spi.c
1 file changed, 65 insertions(+), 15 deletions(-)

git pull ssh://review.coreboot.org:29418/flashrom refs/changes/55/49255/27