Since the register stride should always equal to 2^N, and bit rotation is
much faster than multiplication and division. So introducing the stride
order and using bit rotation to get the offset of the register from the
index to improve the performance.
Signed-off-by: NXiubo Li <lixiubo@cmss.chinamobile.com>
Signed-off-by: NMark Brown <broonie@kernel.org>