egl/dri2: set max values for pbuffer width and height

While these max values were previously fixed for pbuffer creation, this
change makes also eglGetConfigAttrib() return correct values.

Fixes following dEQP tests:

   dEQP-EGL.functional.create_surface.pbuffer.rgb888_no_depth_no_stencil
   dEQP-EGL.functional.create_surface.pbuffer.rgb888_depth_stencil
   dEQP-EGL.functional.create_surface.pbuffer.rgba8888_no_depth_no_stencil
   dEQP-EGL.functional.create_surface.pbuffer.rgba8888_depth_stencil

Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98326
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Cc: "12.0 13.0" <mesa-stable@lists.freedesktop.org>
diff --git a/src/egl/drivers/dri2/egl_dri2.c b/src/egl/drivers/dri2/egl_dri2.c
index 4ed8c12..d9e2ad7 100644
--- a/src/egl/drivers/dri2/egl_dri2.c
+++ b/src/egl/drivers/dri2/egl_dri2.c
@@ -241,6 +241,15 @@
             return NULL;
          break;
 
+      case __DRI_ATTRIB_MAX_PBUFFER_WIDTH:
+         _eglSetConfigKey(&base, EGL_MAX_PBUFFER_WIDTH,
+                          _EGL_MAX_PBUFFER_WIDTH);
+         break;
+      case __DRI_ATTRIB_MAX_PBUFFER_HEIGHT:
+         _eglSetConfigKey(&base, EGL_MAX_PBUFFER_HEIGHT,
+                          _EGL_MAX_PBUFFER_HEIGHT);
+         break;
+
       default:
          key = dri2_to_egl_attribute_map[attrib];
          if (key != 0)