cmd: CONFIG_CMD_LOG select CONFIG_LOG

CONFIG_CMD_LOG without CONFIG_LOG leads to a build error:
‘gd_t {aka volatile struct global_data}’ has no member named
‘default_log_level’

So CMD_LOG should select LOG.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>