msm: Add memory mapped interface for counters

Map the QDSS base address and allow user-space to access it via mmap call.
Add the base address to device tree. Create a character device driver for
the device accessed from user-space.

Change-Id: I76cd542fa9e1b5fc7a6fc9c7cf415351b2c02fed
Signed-off-by: Sheetal Sahasrabudhe <sheetals@codeaurora.org>