power: smb5-lib: Fix DC peripheral access issues

Certain PMICs like pmi632 does not have DC peripheral and hence
DC peripheral access results in R/W error. Fix this by preventing
DC peripheral register access for PMICs that doesn't support them.

Change-Id: I9d8baf4c59cee01b11a6197eae55f101a7a7e5a8
Signed-off-by: Umang Agrawal <uagrawal@codeaurora.org>