ARM: dts: msm: Add support for Qtimer as a avtimer source for SDM845

Qtimer can be used as a source to avtimer. Add right multiplier
and divisor to derive the msecs value out of avtimer tick counts
without using a floating point operation, even when the clock is
running at decimal MHz value (e.g. 19.2MHz etc.).

Change-Id: I1196273060887691e7ff16554ed2ae02290cc492
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>