ARM: dts: msm: Add USB dload cookie relate device node on MSM8937

Linux USB DIAG driver needs to update PID and serial number with
IMEM memory to avoid DIAG port hopping while performing RAMDUMP
collection over USB. Hence add device node entry with IMEM driver
for USB dload cookie imem start address and size.

Change-Id: Idc3bcb2330d1e94381c2c341a989ca083c8fe302
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>