regmap: add regmap_parse_val api

    In some cases, we need regmap's format parse_val function
to do be/le translation according to the bus configuration.
For example, snd_soc_bytes_put() uses regmap to write/read values,
and use cpu_to_be() directly to covert MASK into big endian. This
is a defect, and should use regmap's format function to do it according
to bus configuration.

Signed-off-by: Nenghua Cao <nhcao@marvell.com>
Signed-off-by: Mark Brown <broonie@linaro.org>