USB: sam-ba: add driver for Atmel SAM Boot Assistant (SAM-BA)

Add new driver to access the SAM-BA boot application of Atmel AT91SAM
devices.

The SAM-BA firmware cannot handle merged write requests so we cannot use
the generic write implementation (which uses the port write fifo).

Tested with the SAM-BA 2.10 tools and an Atmel at91sam9260-ek.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Tested-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>