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>
diff --git a/cpu/arm926ejs/at91sam9/lowlevel_init.S b/cpu/arm926ejs/at91sam9/lowlevel_init.S
index 40a3f6a..ec6ad5d 100644
--- a/cpu/arm926ejs/at91sam9/lowlevel_init.S
+++ b/cpu/arm926ejs/at91sam9/lowlevel_init.S
@@ -2,7 +2,7 @@
  * AT91CAP9/SAM9 setup stuff
  *
  * (C) Copyright 2007-2008
- * Stelian Pop <stelian.pop <at> leadtechdesign.com>
+ * Stelian Pop <stelian.pop@leadtechdesign.com>
  * Lead Tech Design <www.leadtechdesign.com>
  *
  * See file CREDITS for list of people who contributed to this