regmap: Bypassing cache when initializing cache

During regcache_init, if client has not passed the
default data of cached register then it is directly
read from the hw to initialize cache. This hw register
read happens before cache ops are initialized and hence
avoiding register read to check for the data available
on cache or not by enabling flag of cache_bypass.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>