PM / devfreq: bimc-bwmon: Add support for version 2

The version 2 of the BIMC BWMON HW doesn't reset the counter to 0 when it
hits the threshold. It also has support for an overflow status register.

Change-Id: I9f18d2153a2e5e762ec9950f26e0e7601468a80a
Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
[avajid@codeaurora.org: made minor styling changes]
Signed-off-by: Amir Vajid <avajid@codeaurora.org>