arm: shmobile: specify PMUs are for ARMv7 CPUs

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

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: Olof Johansson <olof@lixom.net>
Signed-off-by: Olof Johansson <olof@lixom.net>