Add the 12 GP timers nodes present in OMAP2.
Add the 12 GP timers nodes present in OMAP3.
Add the 11 GP timers nodes present in OMAP4.
Add the 7 GP timers nodes present in AM33xx.

Add documentation for timer properties specific to OMAP.

Thanks to Vaibhav Hiremath for creating the AM33xx timer nodes. I have modified
Vaibhav's original nodes adding information on which timers support a PWM
output.

V5 changes:
- Updated timer register sizes for OMAP2/3/4.
- Modified AM335x timer register size to be 1KB instead of 4KB to align with
  HWMOD.
Signed-off-by: NJon Hunter <jon-hunter@ti.com>
Acked-Reviewed-&-Tested-By: Vaibhav Hiremath <hvaibhav@ti.com>
Signed-off-by: NBenoit Cousson <b-cousson@ti.com>