regulator: mem-acc: Do not cache the mem-acc values in software

On some targets both the L1 and L2 ACC configuration
bits are located in the same register. Caching this
register per memory may lead to incorrect ACC values
being programmed. Fix this by always using the latest
ACC configuration from the memory.

Change-Id: Ie3ab96666f6db98559332afd0349d464a5ad1348
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>