drivers: qcom: system_pm: read CVAL to program PDC wake up

The PDC wakeup value must be equal or earlier than the QTimer value that
is set to wake up the system. This is to ensure that the PDC system is
awake before the timer. Read the CVAL from the timer and program the PDC
wakeup value.

Ensure the PDC value is updated after calling tick_broadcast_enter().

Change-Id: I291fd2dd80bed4de19119c548d985ace2ad0c070
Signed-off-by: Lina Iyer <ilina@codeaurora.org>