LoongArch: Migrate to the generic rule for built-in DTB

Commit 654102d ("kbuild: add generic support for built-in boot
DTBs") introduced generic support for built-in DTBs.

Select GENERIC_BUILTIN_DTB when built-in DTB support is enabled.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Author: masahir0y

arch/loongarch/Kbuild

@@ -4,7 +4,6 @@ obj-y += net/
 obj-y += vdso/
 
 obj-$(CONFIG_KVM) += kvm/
-obj-$(CONFIG_BUILTIN_DTB) += boot/dts/
 
 # for cleaning
 subdir- += boot

arch/loongarch/Kconfig

@@ -396,6 +396,7 @@ endchoice
 config BUILTIN_DTB
 	bool "Enable built-in dtb in kernel"
 	depends on OF
+	select GENERIC_BUILTIN_DTB
 	help
 	  Some existing systems do not provide a canonical device tree to
 	  the kernel at boot time. Let's provide a device tree table in the

arch/loongarch/boot/dts/Makefile

@@ -1,5 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
 dtb-y = loongson-2k0500-ref.dtb loongson-2k1000-ref.dtb loongson-2k2000-ref.dtb
-
-obj-$(CONFIG_BUILTIN_DTB)	+= $(addsuffix .dtb.o, $(CONFIG_BUILTIN_DTB_NAME))