openrisc: remove unneeded code in arch/openrisc/Makefile

- LDFLAGS_vmlinux is cleared by the top Makefile

 - 'all: vmlinux' is specified by the top Makefile

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

arch/openrisc/Makefile

@@ -20,7 +20,6 @@
 KBUILD_DEFCONFIG := or1ksim_defconfig
 
 OBJCOPYFLAGS    := -O binary -R .note -R .comment -S
-LDFLAGS_vmlinux :=
 LIBGCC 		:= $(shell $(CC) $(KBUILD_CFLAGS) -print-libgcc-file-name)
 
 KBUILD_CFLAGS	+= -pipe -ffixed-r10 -D__linux__
@@ -50,5 +49,3 @@ else
 BUILTIN_DTB := n
 endif
 core-$(BUILTIN_DTB) += arch/openrisc/boot/dts/
-
-all: vmlinux