pwm: Refactor Qualcomm pwm driver to support upstream pwm framework

Linux 3.10 version includes generic PWM framework support,
therefore update the existing Qualcomm PWM drivers to use the
framework. Rename the qpnp-pwm driver to align with upstream
pwm file nomenclature. Also, revert the pwm header back to linux 3.10.

The changes to the pwm drivers are backward compatible so that they
do not break existing clients. Subsequent patches should include
changes to both PWM drivers and their clients so that usage of
deprecated APIs (i.e. pwm_request) can be removed.

Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>