As stated in Marvell's Functional Specifications in MV-S107021-U0 Rev. A
on page 420 ff. software delays are needed. "SW delay represent a delay
of at least 2 internal clock cycles". These delays are hereby
implemented.

The original kernel driver compensates the needed software delays with
the time the interrupts take.

Signed-off-by: Bastian Stender <bst@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>