nios2: convert makefiles to Kbuild style

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Thomas Chou <thomas@wytron.com.tw>
diff --git a/board/psyent/pk1c20/Makefile b/board/psyent/pk1c20/Makefile
index 0e704a5..286db94 100644
--- a/board/psyent/pk1c20/Makefile
+++ b/board/psyent/pk1c20/Makefile
@@ -5,29 +5,8 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-include $(TOPDIR)/config.mk
 ifneq ($(OBJTREE),$(SRCTREE))
 $(shell mkdir -p $(obj)../common)
 endif
 
-LIB	= $(obj)lib$(BOARD).o
-
-COMOBJS := ../common/AMDLV065D.o
-
-COBJS	:= $(BOARD).o led.o $(COMOBJS)
-
-SRCS	:= $(SOBJS:.o=.S) $(COBJS:.o=.c)
-OBJS	:= $(addprefix $(obj),$(COBJS))
-SOBJS	:= $(addprefix $(obj),$(SOBJS))
-
-$(LIB):	$(obj).depend $(OBJS)
-	$(call cmd_link_o_target, $(OBJS))
-
-#########################################################################
-
-# defines $(obj).depend target
-include $(SRCTREE)/rules.mk
-
-sinclude $(obj).depend
-
-#########################################################################
+obj-y	:= pk1c20.o led.o ../common/AMDLV065D.o