usb: ehci-msm2: Don't always enable hcd->irq for wakeup

Support for enabling the core hcd->irq as a wakeup interrupt
may vary depending on board configuration. In particular, if
the platform has a dedicated IRQ available to wake up the
system, such as async interrupt or D+ GPIO, then they should
obviate needing to enable the core IRQ for wakeup. This change
adds a check on whether the other forms of wakeup are enabled
to decide whether to call enable_irq_wake(hcd->irq).

Change-Id: I53e4e2fb4c70fb26555625bed2ebb2b315a59c1e
Signed-off-by: Jack Pham <jackp@codeaurora.org>