devfreq: bimc_bwmon: Add support to enable BWMON clks

Some BWMON devices requires clocks to be enabled, hence
add necessary support in the bwmon driver to enable the
required clocks if any.

Change-Id: Ie06731f764ff24d602ae2a86dea4f39ce75df800
Signed-off-by: Rama Aparna Mallavarapu <aparnam@codeaurora.org>
[avajid@codeaurora.org: made minor styling changes]
Signed-off-by: Amir Vajid <avajid@codeaurora.org>