usb: dwc3-msm: Mandate pwr_evt_irq only for cores allowing SSPHY suspend

Currently the driver requires pwr_evt_irq to be compulsorily
passed from DT unless the core is dual port. Now consider a core
that does not allow SSPHY autosuspend during operational mode,
instead allowing it only as a part of dwc3_msm_ssphy_autosuspend.
As soon as autosuspend is enabled, there is a chance that
pwr_evt_irq is fired with IN_P3 bit set. Although the driver will
be marking mdwc->in_p3 in the pwr_evt_handler, it will fail to
see IN_P3 bit to be set(because it has been cleared in handler)
during the 5ms wait time in the ssphy_autosuspend function and
prepare_suspend will again set mdwc->in_p3 to 0. This leads to
failure of runtime/system suspend.
Fix this by not passing pwr_evt_irq from DT for the cores which
disable SSPHY autosuspend.

Change-Id: I85ca7e45337fe35c570d163766e7638e11537201
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>