ion: msm: clean up msm custom ioctls

Similar to what was done in core Ion in [$(git rev-parse HEAD)
7ba5b038cc8 "ion: clean up ioctls"], convert the ion ioctls to use _IOW
instead of _IOWR where appropriate, and factor out the copy_from_user.
For the existing incorrect ioctls, add a function to wrap _IOC_DIR to
return the corrected value.

Change-Id: If8ad728fc9d3905d30d722299c4447a00f01992e
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>