[media] v4l2: Introduce V4L2_QCOM_BUF_FLAG_EOS

Add V4L2_QCOM_BUF_FLAG_EOS in an effort to rename V4L2_BUF_FLAG_EOS, as
this is a vendor extension. Once all clients migrate to the QCOM
variant, V4L2_BUF_FLAG_EOS will be removed.

Change-Id: I4ff332f0948990b236a4912286fd202c1e9edaf6
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>