counter: ti-ecap-capture: capture driver support for ECAP

ECAP hardware on TI AM62x SoC supports capture feature. It can be used
to timestamp events (falling/rising edges) detected on input signal.

This commit adds capture driver support for ECAP hardware on AM62x SoC.

In the ECAP hardware, capture pin can also be configured to be in
PWM mode. Current implementation only supports capture operating mode.
Hardware also supports timebase sync between multiple instances, but
this driver supports simple independent capture functionality.

Signed-off-by: Julien Panis <jpanis@baylibre.com>
Link: https://lore.kernel.org/r/20220923142437.271328-4-jpanis@baylibre.com/
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
Link: https://lore.kernel.org/r/25644ce1f2fd15d116977770ede20e024f658513.1664318353.git.william.gray@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>