uio: Add snapshot of MSM sharedmem driver

This is a snapshot of the MSM sharedmem driver as of msm-3.14
commit:
commit 149717c082aab81 ("uio: msm_sharedmem: Add custom mmap") +
sharedmem qmi logic is removed.

The following changes are included:
02d55287 uio: msm_sharedmem: Restrict debugfs write to root.
de961fc7 uio: msm_sharedmem: Return ENOMEM if the shared mem addr
	 is zero.
b974ce64 uio: msm_sharedmem: Add addtional information to debugfs
c46af547 uio: msm_sharedmem: Add support for dynamic shared memory
	 allocation

Change-Id: I49902f018bde1d59d41027b7e46268cc17231a3e
Signed-off-by: Nikhilesh Reddy <reddyn@codeaurora.org>
Signed-off-by: Ritesh Harjani <riteshh@codeaurora.org>
Signed-off-by: Ankit Jain <jankit@codeaurora.org>