soft_rc: sleep between sending individual digits

soft_rc has a feature where a string made up of digits (e.g. "510") is
send as individual digits followed by OK (e.g. "5" + "1" + "0" + OK).
Currently we don't sleep between sending these digits and that seems to
cause problems on HD200. The fix adds a quarter-sec delay between
digits.

Change-Id: If5644f1b48899c399b57f51a2c7f40552ba1f246
1 file changed