powerpc: use always-y instead of extra-y in Makefiles

The extra-y syntax is planned for deprecation because it is similar
to always-y.

When building the boot wrapper, always-y and extra-y are equivalent.
Use always-y instead.

In arch/powerpc/kernel/Makefile, I added ifdef KBUILD_BUILTIN to
keep the current behavior: prom_init_check is skipped when building
only modular objects.

Signed-off-by: Masahiro Yamada <[e-mail]>
Acked-by: Michael Ellerman <[e-mail]>
Signed-off-by: Madhavan Srinivasan <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

arch/powerpc/boot/Makefile

···
 hostprogs	:= addnote hack-coff mktree
 
 targets		+= $(patsubst $(obj)/%,%,$(obj-boot) wrapper.a) zImage.lds
-extra-y		:= $(obj)/wrapper.a $(obj-plat) $(obj)/empty.o \
+always-y	:= $(obj)/wrapper.a $(obj-plat) $(obj)/empty.o \
 		   $(obj)/zImage.lds $(obj)/zImage.coff.lds $(obj)/zImage.ps3.lds
 
 dtstree		:= $(src)/dts
 
 wrapper		:= $(src)/wrapper
-wrapperbits	:= $(extra-y) $(addprefix $(obj)/,addnote hack-coff mktree) \
+wrapperbits	:= $(always-y) $(addprefix $(obj)/,addnote hack-coff mktree) \
 			$(wrapper) FORCE
 
 #############
···
 WRAPPER_BINDIR := /usr/sbin
 INSTALL := install
 
-extra-installed		:= $(patsubst $(obj)/%, $(DESTDIR)$(WRAPPER_OBJDIR)/%, $(extra-y))
+extra-installed		:= $(patsubst $(obj)/%, $(DESTDIR)$(WRAPPER_OBJDIR)/%, $(always-y))
 hostprogs-installed	:= $(patsubst %, $(DESTDIR)$(WRAPPER_BINDIR)/%, $(hostprogs))
 wrapper-installed	:= $(DESTDIR)$(WRAPPER_BINDIR)/wrapper
 dts-installed		:= $(patsubst $(dtstree)/%, $(DESTDIR)$(WRAPPER_DTSDIR)/%, $(wildcard $(dtstree)/*.dts))

arch/powerpc/kernel/Makefile

···
 
 obj-$(CONFIG_PPC_OF_BOOT_TRAMPOLINE) += prom_init.o
 obj64-$(CONFIG_PPC_OF_BOOT_TRAMPOLINE) += prom_entry_64.o
-extra-$(CONFIG_PPC_OF_BOOT_TRAMPOLINE) += prom_init_check
+ifdef KBUILD_BUILTIN
+always-$(CONFIG_PPC_OF_BOOT_TRAMPOLINE) += prom_init_check
+endif
 
 obj-$(CONFIG_PPC64)		+= $(obj64-y)
 obj-$(CONFIG_PPC32)		+= $(obj32-y)