xwayland/eglstream: Demote EGLstream device warning
If no EGLstream capable device is found at startup, Xwayland's EGLstream backend will log an error message "glamor: No eglstream capable devices found".
However, considering that the vast majority of drivers do not implement EGLstream, the lack of EGLstream capable device is more of the norm than the exception.
Change the error message to a simple debug message.
Signed-off-by: Olivier Fourdan ofourdan@redhat.com