nios2: move the install rule to arch/nios2/Makefile

Currently, the install target in arch/nios2/Makefile descends into
arch/nios2/boot/Makefile to invoke the shell script, but it is no
good reason to do so.

arch/nios2/Makefile can run the shell script directly.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

arch/nios2/Makefile

@@ -60,7 +60,8 @@ $(BOOT_TARGETS): vmlinux
 	$(Q)$(MAKE) $(build)=$(nios2-boot) $(nios2-boot)/$@
 
 install:
-	$(Q)$(MAKE) $(build)=$(nios2-boot) BOOTIMAGE=$(KBUILD_IMAGE) install
+	sh $(srctree)/$(nios2-boot)/install.sh $(KERNELRELEASE) \
+	$(KBUILD_IMAGE) System.map "$(INSTALL_PATH)"
 
 define archhelp
   echo  '* vmImage         - Kernel-only image for U-Boot ($(KBUILD_IMAGE))'

arch/nios2/boot/Makefile

@@ -30,6 +30,3 @@ $(obj)/zImage: $(obj)/compressed/vmlinux FORCE
 
 $(obj)/compressed/vmlinux: $(obj)/vmlinux.gz FORCE
 	$(Q)$(MAKE) $(build)=$(obj)/compressed $@
-
-install:
-	sh $(srctree)/$(src)/install.sh $(KERNELRELEASE) $(BOOTIMAGE) System.map "$(INSTALL_PATH)"