ARM: OMAP: Port dmtimers to OMAP2 and implement PWM support

Port dmtimer framework to OMAP2.
Modify the dmtimers API to support setting of PWM configuration and prescaler.
Convert 32 kHz timer and GP timer to use the dmtimer framework.

Signed-off-by: Timo Teras <timo.teras@solidboot.com>
Signed-off-by: Juha Yrjola <juha.yrjola@solidboot.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>