msm: vidc: use managed ioremap

The ioremapped memory (for the register base) is mapped in the probe and
held over the lifetime of the driver. This confuses kmemleak and causes
false positives. Hence switch to devm_ioremap as a hint that it's not
meant to be freed.

CRs-Fixed: 683062
Change-Id: I1a339b8fdb8272e8941f50d6e133ae78f64fd245
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>