broadcom/compiler: implement nir_intrinsic_load_view_index

This is used for multiview's gl_ViewIndex built-in.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12034>

src/broadcom/compiler/v3d_compiler.h

@@ -325,6 +325,11 @@ enum quniform_contents {
          * out-of-bounds accesses into the tile state during binning.
          */
         QUNIFORM_FB_LAYERS,
+
+        /**
+         * Current value of gl_ViewIndex for Multiview rendering.
+         */
+        QUNIFORM_VIEW_INDEX,
 };
 
 static inline uint32_t v3d_unit_data_create(uint32_t unit, uint32_t value)