glsl: Add missing break

Reported by clang's `-Wimplicit-fallthrough`.

Fixes: 328c29d600 ("mesa,glsl,gallium: add GL_OVR_multiview")
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34014>

src/compiler/glsl/ast_type.cpp

@@ -642,7 +642,7 @@ ast_type_qualifier::validate_in_qualifier(YYLTYPE *loc,
           valid_in_mask.flags.q.explicit_numviews = 1;
           break;
       }
-
+      break;
    case MESA_SHADER_TESS_EVAL:
       if (this->flags.q.prim_type) {
          /* Make sure this is a valid input primitive type. */