sh: Replaced "@./mkconfig" for @$(MKCONFIG)

Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>

Makefile

@@ -3049,17 +3049,17 @@ ms7722se_config :	unconfig
 r2dplus_config  :   unconfig
 	@mkdir -p $(obj)include
 	@echo "#define CONFIG_R2DPLUS 1" > $(obj)include/config.h
-	@./mkconfig -a $(@:_config=) sh sh4 r2dplus
+	@$(MKCONFIG) -a $(@:_config=) sh sh4 r2dplus
 
 r7780mp_config: unconfig
 	@mkdir -p $(obj)include
 	@echo "#define CONFIG_R7780MP 1" > $(obj)include/config.h
-	@./mkconfig -a $(@:_config=) sh sh4 r7780mp
+	@$(MKCONFIG) -a $(@:_config=) sh sh4 r7780mp
 
 sh7763rdp_config  :   unconfig
 	@mkdir -p $(obj)include
 	@echo "#define CONFIG_SH7763RDP 1" > $(obj)include/config.h
-	@./mkconfig -a $(@:_config=) sh sh4 sh7763rdp
+	@$(MKCONFIG) -a $(@:_config=) sh sh4 sh7763rdp
 
 sh7785lcr_config  :   unconfig
 	@ >include/config.h