greybus: bootrom: send timeout in milliseconds to gb_bootrom_set_timeout()

Rename NEXT_REQ_TIMEOUT_J to NEXT_REQ_TIMEOUT_MS and store the timeout
in milliseconds instead of jiffies.

Suggested-by: Alex Elder <alex.elder@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>