board/raspberrypi: bump to use Linux 3.10

The new 'stable' branch of the Raspberry Pi kernel is now based
on the Linux 3.10 branch (currently 3.10.22), so bump both the
kernel version for the toolchain headers, and for the target.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>