egl: Replace KHR_surfaceless_* extensions with KHR_surfaceless_context

egl: Replace KHR_surfaceless_* extensions with KHR_surfaceless_context

KHR extension name is reserved for Khronos ratified extensions, and there is
no such thing as EGL_KHR_surfaceless_{gles1,gles2,opengl}.  Replace these
three extensions with EGL_KHR_surfaceless_context since that extension
actually exists.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Chad Versace <chad.versace@linux.intel.com>