ARM: dts: update memory cma reservations for mdm9640

Update the memory reservations for audio heap and modem
pil regions by using the upstream kernel reservation
device tree compatible strings.

Change-Id: I4b4f139795f31b7296275b7a2bee53e1bf852a11
Signed-off-by: Abhimanyu Kapur <abhimany@codeaurora.org>