ion : Merge ion changes for msm-kona kernel upgrade

Merge all ion changes from msm-4.14 to msm-kona as of:
'commit a15a4042 ("ion: Ensure ion_buffer fields
are initialized")'

Change-Id: I1a5f300158b3cc4f5b9cc4cf888a8678f8746152
Signed-off-by: Swathi Sridhar <swatsrid@codeaurora.org>