glsl: correct indentation of comment, Trivial.

Signed-off-by: Tapani Pälli <tapani.palli@intel.com>

src/glsl/linker.cpp

@@ -2571,7 +2571,7 @@ add_interface_variables(struct gl_shader_program *shProg,
              var->data.location != SYSTEM_VALUE_VERTEX_ID_ZERO_BASE &&
              var->data.location != SYSTEM_VALUE_INSTANCE_ID)
             continue;
-            /* FALLTHROUGH */
+         /* FALLTHROUGH */
       case ir_var_shader_in:
          if (programInterface != GL_PROGRAM_INPUT)
             continue;