MIPS: fix *-pkg builds for loongson2ef platform

Hello, stable maintainers.

I'd like to request the change made by cca2aac8acf470b01066f559acd7146fc4c32ae8 be applied to the 5.15 and 5.14 series so as to address the build failure. That patch doesn't apply to 5.14 as-is so I am attaching a backported version of the patch that does.

From 1817d870345062bbc91b35cd2324556d27ce8010 Mon Sep 17 00:00:00 2001
From: Masahiro Yamada <[email protected]>
Date: Sun, 14 Nov 2021 07:47:31 -0800
Subject: [PATCH] MIPS: fix *-pkg builds for loongson2ef platform

commit cca2aac8acf470b01066f559acd7146fc4c32ae8 upstream.

Since commit 805b2e1d427a ("kbuild: include Makefile.compiler only when compiler is needed"), package builds for the loongson2f platform fail.

  $ make ARCH=mips CROSS_COMPILE=mips64-linux- lemote2f_defconfig bindeb-pkg
    [ snip ]
  sh ./scripts/package/builddeb
  arch/mips/loongson2ef//Platform:36: *** only binutils >= 2.20.2 have needed option -mfix-loongson2f-nop.  Stop.
  cp: cannot stat '': No such file or directory
  make[5]: *** [scripts/Makefile.package:87: intdeb-pkg] Error 1
  make[4]: *** [Makefile:1558: intdeb-pkg] Error 2
  make[3]: *** [debian/rules:13: binary-arch] Error 2
  dpkg-buildpackage: error: debian/rules binary subprocess returned exit status 2
  make[2]: *** [scripts/Makefile.package:83: bindeb-pkg] Error 2
  make[1]: *** [Makefile:1558: bindeb-pkg] Error 2
  make: *** [Makefile:350: __build_one_by_one] Error 2

The reason is because "make image_name" fails.

  $ make ARCH=mips CROSS_COMPILE=mips64-linux- image_name
  arch/mips/loongson2ef//Platform:36: *** only binutils >= 2.20.2 have needed option -mfix-loongson2f-nop.  Stop.

In general, adding $(error ...) in the parse stage is troublesome, and it is pointless to check toolchains even if we are not building anything. Do not include Kbuild.platform in such cases.

---
 arch/mips/Makefile | 2 ++
 1 file changed, 2 insertions(+)

index 653befc1b..0dfef0bea 100644
@@ -254,7 +254,9 @@ endif
 #
 # Board-dependent options and extra files
 #
+ifdef need-compiler
 include arch/mips/Kbuild.platforms
+endif
 
 ifdef CONFIG_PHYSICAL_START
 load-y					= $(CONFIG_PHYSICAL_START)

2.33.1