ARM: mach-shmobile: Introduce shmobile_setup_delay()

Add the function shmobile_setup_delay() to let platforms
configure their maximum loops per jiffy delay. With this
jiffies calculation done the dependency on early timer
is removed.

In the future this allows us to assign timers
using the regular driver model via the device tree.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>