regulator: cpr3: fix panic callback failure in interrupt context

The kernel panic could happen in CPU interrupt context. CPR3 panic
callback function does ioremap which cannot be executed in an interrupt
context. Fix the issue by doing a ioremap during driver initialization.

CRs-Fixed: 1056786
Change-Id: I191127fafb26bcf10ea25f972fe5af122debf292
Signed-off-by: Tirupathi Reddy <tirupath@codeaurora.org>