ARM: versatile: move integrator/realview/vexpress to versatile

These are all fairly small platforms by now, and they are
closely related. Just move them all into a single directory.

Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Liviu Dudau <liviu.dudau@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>