ARM: 6153/1: nomadik MTU to use dynamic shift and mult assignment

This removes the hard-coded shift values for the MTU timer, since
the different platforms using this has very different running
frequencies doing this dynamically is a better idea. Also take
this opportunity to make a more through shutdown of the MTU
clockevent when requested.

Acked-by: Alessandro Rubini <rubini@unipv.it>
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>