Fix @ -> <at> substitution

When applying the AT91CAP9 patches upstream, something transformed
the '@' character into the ' <at> ' sequence.

The patch below restores the original form in all the places where
it has been modified (the AT91CAP9 files, the AT91SAM9260 files which
were copied from AT91CAP9, and a couple of other files where the
' <at> ' sequence was present).

Signed-off-by: Stelian Pop <stelian@popies.net>