OMAP-TEST: TIMER: Add Request Test

Add a timer request test to test the timer request APIs ...

- omap_dm_timer_request()
- omap_dm_timer_request_by_cap()
- omap_dm_timer_request_specific()

Note that omap_dm_timer_request_specific() is not supported when device
tree is present and so is only tested when booting without device tree.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
OMAP-TEST: TIMER: Add match interrupt test

Adds test for timer match interrupt feature.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
OMAP-TEST: TIMER: Interrupt fixes

Several minor interrupt fixes for the timer tests, including ...

1. Using the new omap_dm_timer_set_int_disable() API to disable
   interrupts instead of the omap_dm_timer_set_int_enable() API because
   this API does not work for all timer instances.
2. Disable interrupts prior to stopping the timer, so there is no chance
   of an interrupt occurring just as we are stopping the timer and
   generating an exception because the clocks are disabled when the
   interrupt handler runs.
3. Only acknowledge the interrupt, if a valid interrupt occurred.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
OMAP-TEST: Add README

Add README file with build and usage instructions.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
OMAP-TEST: TIMER: Remove unnecessary function

The function omap_timer_request_one() is not particularly useful or
necessary and so remove it!

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
OMAP-TEST: TIMER: DT fix for missing context loss check

When booting with device-tree, the function pointer to the timer context
loss check routine is not initialised. Therefore, when booting with
device-tree, the timer driver has no way to determine if the context has
been lost and needs to be restored. Workaround this for now by keeping
the timer on when in use.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>