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/Makefile b/cpu/arm926ejs/at91sam9/Makefile
index 203abc2..44cde1a 100644
--- a/cpu/arm926ejs/at91sam9/Makefile
+++ b/cpu/arm926ejs/at91sam9/Makefile
@@ -1,6 +1,6 @@
 #
 # (C) Copyright 2000-2008
-# Wolfgang Denk, DENX Software Engineering, wd <at> denx.de.
+# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
 #
 # See file CREDITS for list of people who contributed to this
 # project.