The native display parameter to eglGetPlatformDisplayEXT has type void*.
When building with -DUSE_OZONE the native display type is intptr_t so
a cast is needed.

BUG=angleproject:1297

Change-Id: I947f5f9016926b6e3d590a2e29b5ee1fc883384d
Reviewed-on: https://chromium-review.googlesource.com/323471Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Frank Henigman <fjhenigman@chromium.org>
Commit-Queue: Frank Henigman <fjhenigman@chromium.org>
Tested-by: Frank Henigman <fjhenigman@chromium.org>