cmd: log: Add commands to manipulate filters

This adds several commands to add, list, and remove log filters. Due to the
complexity of adding a filter, `log filter-list` uses options instead of
positional arguments.

These commands have been added as subcommands to log by using a dash to
join the subcommand and subsubcommand. This is stylistic, and they could be
converted to proper subsubcommands if it is wished.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index 9f36290..1595de9 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -2239,6 +2239,7 @@
 config CMD_LOG
 	bool "log - Generation, control and access to logging"
 	select LOG
+	select GETOPT
 	help
 	  This provides access to logging features. It allows the output of
 	  log data to be controlled to a limited extent (setting up the default