at91bootstrap3: new package

at91bootstrap3: new package

Note that this new package, at91bootstrap3, is being added alongside the
existing at91bootstrap. This was suggested by Thomas Petazzoni, whose
comments on the mailing list are quoted below.

  For this package, I am not sure we can do a simple version bump. Since
  there is (was?) no upstream for AT91Bootstrap 1.x, many
  vendors/companies had to maintain their patches on top of AT91Bootstrap
  1.x. See for example
  board/calao/usb-a9263/at91bootstrap-1.16-usb-a9263.patch. Therefore,
  removing AT91Bootstrap 1.x from the tree will prevent those platforms
  to work. I know people should upgrade, but AT91Bootstrap 3.x is quite
  significantly different, so the porting effort is not that simple.

  Therefore, I'm wondering whether we should kee at91bootstrap as it is,
  and create a separate package at91bootstrap3 for the 3.x generation.

Signed-off-by: Simon Dawson <spdawson@gmail.com>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>