tools: updater: iterate via string instead of auto
tools: updater: iterate via string instead of auto

Use a std::string declaration instead of auto to add backwards
compatibility and because it's clearly only ever going to be a string
and we're doing a c-string check.

Change-Id: I89bf9076cdc711209a75684a984a39c058367355
Signed-off-by: Patrick Venture <36c53fa43f47f3fd67cb2fc38031827244d18a1f@google.com>

openbmc/phosphor-ipmi-flash