buildroot

DEVELOPERS: Update email address

I am leaving Xilinx so to avoid future bounces update my email address
to my personal email address.

Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>
Signed-off-by: Alistair Francis <alistair@alistair23.me>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>