ARM: gemini: convert to GENERIC_CLOCKEVENTS

This converts the gemini machine to use generic clockevents
by rewriting the timer driver.

Cc: arm@kernel.org
Cc: Hans Ulli Kroll <ulli.kroll@googlemail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>