Separate wait() and enumerate() methods from struct usbhost_driver_s and move to new interface, struct usbhost_connection_s.  This is part of the necessary restructuring of the USB host interface to support multiple root hub ports.

Add untested OHCI driver for the SAMA5; structure naming and header files for USB host initialization prototypes

Extend the virtual-to-physical address conversion logic to handle NFS SRM, UDPH SRAM, and external SRAM and PSRAM.

SAMA5: Use RDR/TDR registers for DMA, not FIFO registers; change DMA bit settings to match Atmel example.  Still no DMA

SAMA5 DMA: Need to flush caches; DMA channel depends upon direction of DMA; the maximum transfer size in bytes depends on the number of bytes per transfer

SAMA5: Add PIO interrupt support.  Massive name changes for consistency in PIO vs GPIO naming.  SAMA5D3x-EK:  Add support for SD card detection PIO interrupts

SAMA5:  SPI Driver + AT25 FLASH work; SAM3/4:  Correct an error, SPI will not be correctly configured if CONFIG_SPI_OWNBUS=n

Standard configuration variables used to enable interupt controller debug; SAMA5: Correct handling of spurious interrupts