The 'LoadToNative' copy is the only one that should be considered a
non-conversion. For depth formats, we should be clamping on SetData
and CopyImage calls, so this changes the flags for two of the
depth formats, but won't affect behaviour since the conversion bit
is never check for depth/stencil formats.

This allows us to remove the 'requiresConversion' bit from the data.

BUG=angleproject:1455

Change-Id: I739ecc54406d65049caad7851ffd51d7cb777946
Reviewed-on: https://chromium-review.googlesource.com/367693Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>