Add run_command_repeatable()

run_command() returns 0 on success and 1 on error. However, there are some
invocations which expect 0 or 1 for success (not repeatable or repeatable)
and -1 for error; add run_command_repeatable() for this purpose.

Signed-off-by: Thomas Betker <thomas.betker@rohde-schwarz.com>
Acked-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>