ANDROID: GKI: drivers: clksource: Add API to return cval

Sleep driver needs to program the absolute clock value for next expiry
into pdc register for system wake up. Add an API to read the cval low
and high counters.

Signed-off-by: Channagoud Kadabi <ckadabi@codeaurora.org>
Bug: 152635062
Test: build
(cherry picked from commit ee514e90)
[surenb: replaced out-of-tree readl_relaxed_no_log with functionally
identical in-tree readl_relaxed]
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Change-Id: I1244c31c8a2717a6f2002cac3b26ee3526409058
Merged-In: I1244c31c8a2717a6f2002cac3b26ee3526409058