Change in coreboot[master]: elogtool: add "clear" command

[Ricardo Quesada (Code Review)]

Attention is currently required from: Ricardo Quesada, Jack Rosenthal.
Hello build bot (Jenkins), Furquan Shaikh, Jack Rosenthal,

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

https://review.coreboot.org/c/coreboot/+/56883

to look at the new patch set (#14).

Change subject: elogtool: add "clear" command
......................................................................

elogtool: add "clear" command

Adds "clear" command to cbfsutil/elogtool tool.
"clear" clears the RW_ELOG region by using either:
 * flashrom if no file is provided
 * or using file write if an input file is provided.

The region is filled with ELOG_TYPE_EOL. And a
ELOG_TYPE_LOG_CLEAR event is inserted.

Additionally, it does a minor cleanup to command "list", like:
 * use buffer_end()
 * add "list" to the cmds struct
 * and make elog_read() very similar to elog_write()

Usage:
$ elogtool clear

BUG=b:172210863
TEST=elogtool clear && elogtool list
     elogtool clear -f invalid.raw
     elogtool clear -f valid.raw

Change-Id: Ia28a6eb34c82103ab078a0841b022e2e5e430585
Signed-off-by: Ricardo Quesada 
---
M util/cbfstool/elogtool.c
M util/cbfstool/eventlog.c
M util/cbfstool/eventlog.h
3 files changed, 175 insertions(+), 48 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/83/56883/14