pwm: omap-dmtimer: Add debug message for effective period and duty cycle

After going through the math and constraints checking to compute load
and match values, it is helpful to know what the resultant period and
duty cycle are.

Signed-off-by: David Rivshin <drivshin@allworx.com>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>