qpnp: revid: Add support to read FAB ID for PMICOBALT

PMICOBALT supports reading the FAB ID from the REVID
peripheral. Add an optional property qcom,fab-id-valid
to check if support for FAB ID is available in the
REVID peripheral for the PMIC.

Change-Id: If8212618baa7533b008228a71740acf1d6c72a52
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>