pwm: qpnp: Read dtest configuration before checking mode

In certain cases like PWM configuration handoff from the bootloader,
it's not required to configure the PWM channel during probe. So
mode-select will not be specified. Without mode-select, driver will
skip reading dtest related configuration. However this has to be
still read from the device tree and stored for controlling the
PWM configuration further. Hence move reading the dtest related
configuration before reading the mode-select.

Change-Id: Ia3378d98e172b55f47ac6acebbc4e8c525cb963e
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>