util/cbmem: Add --loglevel option to restrict console printing by level

util/cbmem: Add --loglevel option to restrict console printing by level

This patch adds a new --loglevel option to the CBMEM utility which can
be used either numerically (e.g. `cbmem -1 --loglevel 6`) or by name
(e.g. `cbmem -c --loglevel INFO`) to restrict the lines that will be
printed from the CBMEM console log to a maximum loglevel. By default,
using this option means that lines without a loglevel (which usually
happens when payloads or other non-coreboot components add their own
logs to the CBMEM console) will not be printed. Prefixing a `+`
character to the option value (e.g. `--loglevel +6` or
`--loglevel +INFO`) can be used to change that behavior.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: I8458027083246df5637dffd3ebfeb4d0a78deadf
Reviewed-on: https://review.coreboot.org/c/coreboot/+/61779
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>