drm/dp_helper: don't return EPROTO for defers (v2)
drm/dp_helper: don't return EPROTO for defers (v2)

If we get a msg.reply of REPLY_DEFER, we also get an err of 0
so we fail reads with 0 < size and return -EPROTO instead of trying
again.

v2: same fix in i2c code.

Found writing MST support.

Reviewed-by: Jani Nikula <ba783f3beccaedfda693f41a15407d612a629408@intel.com>
Reviewed-by: Thierry Reding <3055038c414aef68bf32c33b8118623e7554e0f2@nvidia.com>
Signed-off-by: Dave Airlie <f2295d84e358395675bc8031be58672073ae065e@redhat.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs