Two consecutive eglBindTexImage calls on the same buffer (texture)
would eventually result in a crash if the texture is released before
the egl surfaces, so this assert is meant to perform an early
detection of a harder to detect future issue.

Bug chromium:932986 chromium:929088

Change-Id: I10b3892fe06d491c8a0a09dec84678b25f49c6ab
Reviewed-on: https://swiftshader-review.googlesource.com/c/25128Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>