ARM: realview: add generic config options

This adds a few features that are available on some
or all of the RealView but never made it into the SMP
defconfig file:

- Full tickless idle
- High resolution timers
- Perf events and HW perf events from the PMU
- MTD AFS partition handling
- MTD ROM partition handling
- USB and ISP1760 USB driver

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>