Add CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC to allow architectures
to request having modules data in vmalloc area instead of module area.

This is required on powerpc book3s/32 in order to set data non
executable, because it is not possible to set executability on page
basis, this is done per 256 Mbytes segments. The module area has exec
right, vmalloc area has noexec.

This can also be useful on other powerpc/32 in order to maximize the
chance of code being close enough to kernel core to avoid branch
trampolines.

Cc: Jason Wessel <jason.wessel@windriver.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
[mcgrof: rebased in light of kernel/module/kdb.c move]
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>