arm: realview: specify PMU types

Now that we can specify which PMU variant we're likely to deal with, do
so in the realview board code. This will allow us to split the ARMv6,
ARMv7, and XScale PMU drivers.

The Realview EB may be used with ARMv6 or ARMv7 CPUs, but luckily
there's only a single ARMv7 CPU, so we can match that explicitly to
determine whether or not we have an ARMv7 PMU.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Olof Johansson <olof@lixom.net>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Olof Johansson <olof@lixom.net>