powerpc: move the install rule to arch/powerpc/Makefile

Currently, the install target in arch/powerpc/Makefile descends into
arch/powerpc/boot/Makefile to invoke the shell script, but there is no
good reason to do so.

arch/powerpc/Makefile can run the shell script directly.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210729141937.445051-3-masahiroy@kernel.org

arch/powerpc/Makefile

@@ -407,7 +407,8 @@ endef
 
 PHONY += install
 install:
-	$(Q)$(MAKE) $(build)=$(boot) install
+	sh -x $(srctree)/$(boot)/install.sh "$(KERNELRELEASE)" vmlinux \
+	System.map "$(INSTALL_PATH)"
 
 archclean:
 	$(Q)$(MAKE) $(clean)=$(boot)

arch/powerpc/boot/Makefile

@@ -444,12 +444,6 @@ $(obj)/zImage:		$(addprefix $(obj)/, $(image-y))
 $(obj)/zImage.initrd:	$(addprefix $(obj)/, $(initrd-y))
 	$(Q)rm -f $@; ln $< $@
 
-# Only install the vmlinux
-install:
-	sh -x $(srctree)/$(src)/install.sh "$(KERNELRELEASE)" vmlinux System.map "$(INSTALL_PATH)"
-
-PHONY += install
-
 # anything not in $(targets)
 clean-files += $(image-) $(initrd-) cuImage.* dtbImage.* treeImage.* \
 	zImage zImage.initrd zImage.chrp zImage.coff zImage.holly \