gatt: add a user data field to gattClientRead() and gattCliReadCbk()

BUG=b:134425062
TEST=built

Change-Id: Ia2ae97485d90228ef0263c486c23e05ffbcb809e
Reviewed-on: https://chromium-review.googlesource.com/1747742
Tested-by: Miao-chen Chou <mcchou@chromium.org>
Commit-Ready: Miao-chen Chou <mcchou@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Sonny Sasaka <sonnysasaka@chromium.org>
4 files changed