ARM: dts: msm: Add memory-mapped timer for APQ8084

Even though APQ8084 supports the CP15 system timer, the
memory-mapped timer is needed to store the state of the
system timer during deep idle. Add the device tree entries
needed to define the configuration of the memory-mapped
timer instance.

Change-Id: I4bd87d98d4f43eb2af692ee47b1c9c15af46bc8a
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>