video: adf: fix ADF_MAX_ATTACHMENTS declaration

Userspace-facing ADF_MAX_ATTACHMENTS must be in terms of
userspace-facing struct adf_attachment_config

Change-Id: Iaaddcd6366f13b3e52eb3911efcfff8a61e0b225
Signed-off-by: Greg Hackmann <ghackmann@google.com>
Git-commit: ccf0b45b743f5075143beccf8beca8fd9e988ef1
Git-Repo: https://android.googlesource.com/kernel/common.git


Signed-off-by: Ian Maund <imaund@codeaurora.org>