usb: musb: dsps: do not set is_active on the first drvbus interrupt

Quite early on init there is an vbus / drvvbus interrupt comming and the
dsps code sets is_active to one. As a result we see a lot of

|musb_bus_suspend 2459: trying to suspend as a_wait_bcon while active

until a device is plugged in with pm_runtime enabled in the kernel.
After checking davinci, am35, da8xx I noticed that dsps is actually the
only one doing this.
So remove it and we won't flooded with mesages and the idle port can be
suspended.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>