msm: clock-pll: Support dynamically mapped register space

Clock controller registers may be dynamically mapped into
memory in some clock drivers. Since those drivers are still
expected to re-use clock-pll code, support dynamically
mapped register spaces.

Change-Id: Iaf07f213d2bef64a68564b698a2536e611d724bd
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>