thermal: Add MSM POP memory thermal driver

Add msm_popmem-tm driver for monitoring the temperature of
MSM POP memory. The temperature reported is based off of
the refresh rate of the POP memory. The temperatures
are reported as follows:

Low Temperature: 25C
Normal Temperature: 50C
High (out of range) Temperature: 85C

Change-Id: Id299ac574745b2a5580ff9999dd514481468c184
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
Signed-off-by: David Brown <davidb@codeaurora.org>