Some drivers and other bsp code not only poll the
register with timeout but also required to delay
on each transaction.
This patch add that requirement by adding sleep_us
variable so-that read_poll_timeout now support
delay as well.
This change is referenced from Linux from below commit:
commit <5f5323a14cad19323060a8cbf9d96f2280a462dd> ("iopoll:
introduce read_poll_timeout macro")
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
c094e219a8