PM / devfreq: bimc-bwmon: Add support for version 4

The version 4 of the BIMC BWMON hardware now has provisions for
counting bytes transferred at a high sampling rate.

Modify the existing driver and governor algorithm to
take advantage of that.

Change-Id: I5080297aef7e310d5c1a19098c177ddecb729c25
Signed-off-by: Rohit Gupta <rohgup@codeaurora.org>
Signed-off-by: David Keitel <dkeitel@codeaurora.org>