kbuild: fix kernel-devel RPM package and linux-headers Deb package

Since commit fe66b5d2 ("kbuild: refactor kernel-devel RPM package
and linux-headers Deb package"), the kernel-devel RPM package and
linux-headers Deb package are broken.

I double-quoted the $(find ... -type d), which resulted in newlines
being included in the argument to the outer find comment.

  find: 'arch/arm64/include\narch/arm64/kvm/hyp/include': No such file or directory

The outer find command is unneeded.

Fixes: fe66b5d2 ("kbuild: refactor kernel-devel RPM package and linux-headers Deb package")
Reported-by: Karolis M <k4rolis@protonmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>

scripts/package/install-extmod-build

@@ -20,7 +20,7 @@ mkdir -p "${destdir}"
 	find "arch/${SRCARCH}" -maxdepth 1 -name 'Makefile*'
 	find include scripts -type f -o -type l
 	find "arch/${SRCARCH}" -name Kbuild.platforms -o -name Platform
-	find "$(find "arch/${SRCARCH}" -name include -o -name scripts -type d)" -type f
+	find "arch/${SRCARCH}" -name include -o -name scripts -type d
 ) | tar -c -f - -C "${srctree}" -T - | tar -xf - -C "${destdir}"
 
 {