Relying on the access time of peripherals is unreliable - it depends
on the speed of the CPU and the bus.  On Versatile Express, these
timeouts were expiring, causing the driver to fail.

Add udelay(1) to ensure that they don't expire early, and adjust
timeouts to give a reasonable margin over the response times.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>