atmel: Drop README.at91-soc

This issue covered by this doc appears to be fixed, so let's remove the
README.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: York Sun <york.sun@nxp.com>
Acked-by: Andreas Bießmann <andreas@biessmann.org>
1 file changed