Change in flashrom[master]: lspcon_i2c_spi: support a devpath option

[Peter Marheine (Code Review)]

Attention is currently required from: Edward O'Callaghan, Peter Marheine.
Hello build bot (Jenkins), Edward O'Callaghan, Angel Pons,

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

https://review.coreboot.org/c/flashrom/+/51967

to look at the new patch set (#4).

Change subject: lspcon_i2c_spi: support a devpath option
......................................................................

lspcon_i2c_spi: support a devpath option

Some callers may find it easier to provide the path to an I2C device
at which to communicate with the device, rather than specify the bus
number- doing so might involve trying to parse a path to extract the
number only for flashrom to do the reverse, which is error-prone and
unnecessary.

This change adds support for a `devpath` option, continuing to
allow `bus` and requiring only one of them be specified.

TEST=Verified --flash-size outputs correct values with both
     devpath=/dev/i2c-7 and bus=7, as well as noting that one is
     required if neither is specified and only one may be specified
     if both are given.

Signed-off-by: Peter Marheine 
Change-Id: Id2adf8a307b9205ce5e5804a6c3e22f19d0c34c9
---
M i2c_helper.h
M i2c_helper_linux.c
M lspcon_i2c_spi.c
3 files changed, 78 insertions(+), 50 deletions(-)

git pull ssh://review.coreboot.org:29418/flashrom refs/changes/67/51967/4