post: convert makefiles to Kbuild style

This commit also deletes post/rules.mk,
which in not necessary any more.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/post/lib_powerpc/Makefile b/post/lib_powerpc/Makefile
index efa1fb2..f19fea3 100644
--- a/post/lib_powerpc/Makefile
+++ b/post/lib_powerpc/Makefile
@@ -4,13 +4,12 @@
 #
 # SPDX-License-Identifier:	GPL-2.0+
 #
-include $(TOPDIR)/config.mk
 
-LIB	= libpost$(ARCH).o
+CPPFLAGS += -I$(TOPDIR)
 
-AOBJS-$(CONFIG_HAS_POST)	+= asm.o
-COBJS-$(CONFIG_HAS_POST)	+= cpu.o cmp.o cmpi.o two.o twox.o three.o threex.o
-COBJS-$(CONFIG_HAS_POST)   += threei.o andi.o srawi.o rlwnm.o rlwinm.o rlwimi.o
-COBJS-$(CONFIG_HAS_POST)	+= store.o load.o cr.o b.o multi.o string.o complex.o
+obj-$(CONFIG_HAS_POST) += asm.o
+obj-$(CONFIG_HAS_POST) += cpu.o cmp.o cmpi.o two.o twox.o three.o threex.o
+obj-$(CONFIG_HAS_POST) += threei.o andi.o srawi.o rlwnm.o rlwinm.o rlwimi.o
+obj-$(CONFIG_HAS_POST) += store.o load.o cr.o b.o multi.o string.o complex.o
 
-include $(TOPDIR)/post/rules.mk
+obj-$(CONFIG_HAS_POST) += fpu/