render/egl: add check for EGL_KHR_surfaceless_context
render/egl: add check for EGL_KHR_surfaceless_context

As surfaces are no longer going to be used for wlr_egl, I may as well just go and add this check as it is needed for safety whenever surface-less rendering is being used.

swaywm/wlroots,swaywm/wlroots,SirCmpwn/wlroots