egl: fix OpenGL 3.1 context creation

egl: fix OpenGL 3.1 context creation

>From the EGL_KHR_create_context spec:

   "* If OpenGL 3.1 is requested, the context returned may implement
       any of the following versions:

         * Version 3.1. The GL_ARB_compatibility extension may or may
           not be implemented, as determined by the implementation.
         * The core profile of version 3.2 or greater."

Fixes CTS tests:

    dEQP-EGL.functional.create_context_ext.gl_31.rgb888_depth_stencil
    dEQP-EGL.functional.create_context_ext.robust_gl_31.rgb888_depth_stencil
    dEQP-EGL.functional.create_context_ext.gl_31.rgb888_depth_no_stencil
    dEQP-EGL.functional.create_context_ext.robust_gl_31.rgb888_depth_no_stencil
    dEQP-EGL.functional.create_context_ext.gl_31.rgba8888_depth_no_stencil
    dEQP-EGL.functional.create_context_ext.gl_31.rgb888_no_depth_no_stencil
    dEQP-EGL.functional.create_context_ext.robust_gl_31.rgba8888_depth_no_stencil
    dEQP-EGL.functional.create_context_ext.robust_gl_31.rgb888_no_depth_no_stencil
    dEQP-EGL.functional.create_context_ext.gl_31.rgba8888_no_depth_no_stencil
    dEQP-EGL.functional.create_context_ext.robust_gl_31.rgba8888_no_depth_no_stencil
    dEQP-EGL.functional.create_context_ext.gl_31.rgba8888_depth_stencil
    dEQP-EGL.functional.create_context_ext.robust_gl_31.rgba8888_depth_stencil

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>