target-arm: Make '-cpu any' available in linux-user mode only

Make the 'any' CPU for target-arm available only in linux-user mode.
The ARM target provides a CPU named "any", which turns on support for
all user-level instruction set extensions we know about. This is
intended for linux-user emulation mode, where it is the default CPU type.
It makes no sense to try to use this for system emulation, since we don't
initialize it with any system-level information like feature register
values or implementation specific cp15 registers. (Unsurprisingly, some
boards won't boot at all, though you might get lucky in some cases where
the guest doesn't happen to prod things that aren't there.)

Prevent users from making this command line error by removing the
CPU definition from the softmmu build.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Message-id: 1378213995-12945-1-git-send-email-peter.maydell@linaro.org
