at91: at91-ohci: support overcurrent notification

at91: at91-ohci: support overcurrent notification

Several USB power switches (AIC1526 or MIC2026) have a digital output
that is used to notify that an overcurrent situation is taking
place. This digital outputs are typically connected to GPIO inputs of
the processor and can be used to be notified of those overcurrent
situations.

Therefore, we add a new overcurrent_pin[] array in the at91_usbh_data
structure so that boards can tell the AT91 OHCI driver which pins are
used for the overcurrent notification, and an overcurrent_supported
boolean to tell the driver whether overcurrent is supported or not.

The code has been largely borrowed from ohci-da8xx.c and
ohci-s3c2410.c.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>