Fix a bug in the FAT unbind() logic.  There were problems with the way certain internal list handling was implemented.  The end result is that newly opened or cloned file structures were never being added to the list of open files.  So when the unmount() happens, it always looked like there were not open files and a crash could ensue.

Pass the umount2() flags to every unbind() implementation.  That is where the the decision to umount or not will be made.

and this one https://www.sdcard.org/downloads/pls/simplified_specs/part1_410.pdf) shows that ACMD23
must be preceeded with CMD55 command as any other ACMD commands.

Also, after the block reading wait loop must be inserted before writing the next block of data to
the sd card

From Dmitry Nikolaev via Jussi Kivilinna

drivers/serial: Report correct number of bytes free in serial buffer with FIONWRITE.  From Jussi Kivilinna.

SAMV71: Quick'n'dirty port of the SAMA5 SSC driver to the SAM7.  The IP is compatible but there are still some DMA- and Cache-related issues that need to be worked out.