Only use UInt gl_ViewID_OVR from ESSL3
OVR multiview should not be exposed in ESSL1

Bug: angleproject:3822
Change-Id: Ia9d6247e3a717b06db26f1d436e2b33336b12a7d
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1759143Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Clemen Deng <clemendeng@google.com>