common: command: trivial coding style fixes

- Do not insert a whitespace between a function name and
   an open paranthesis
 - Fix comment style
 - Do not split an error message into multiple lines
   even if it exceeds 80 columns
 - Do not split "for" statement where it fits in 80 columns
 - Do not use assignment in if condition

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Simon Glass <sjg@chromium.org>