Install targets (install, zinstall, uinstall) on arm have a dependency
to vmlinux. This may cause parts of the kernel to be rebuilt during
installation. We must avoid this since this may run as root. Install
targets "ABSOLUTELY MUST NOT MODIFY THE SOURCE TREE." as Linus
emphasized this in:

 http://lkml.org/lkml/2013/7/10/600

So on arm and maybe other archs we need the same as for x86:

 1648e4f8 x86, kbuild: make "make install" not depend on vmlinux

This patch fixes this for arm. Dependencies are removed and instead a
check to install.sh is added for the files that are needed.

This issue was uncovered by this build error where the -j option is
used in conjunction with install targets:

 $ make <makeflags>
 $ make <makeflags> zinstall
 ...
   DEPMOD
 Usage: .../scripts/depmod.sh /sbin/depmod <kernelrelease>

(INSTALL_MOD_PATH and INSTALL_PATH variables set, so no root perms
required in this case.)

The problem is that zinstall on arm due to its dep...