Fix attribution in ChangeLog

While going through some history, I noticed that I'd committed one
of Alan's changes with my email address rather than his.  Sorry for
the screw-up.

From-SVN: r229366

gcc/ChangeLog

@@ -31128,7 +31128,7 @@
 	* config/aarch64/aarch64.c (aarch64_simd_attr_length_rglist)
 	(aarch64_reverse_mask): New functions.
 
-2015-01-21  Richard Sandiford  <richard.sandiford@arm.com>
+2015-01-21  Alan Hayward  <alan.hayward@arm.com>
 
 	* config/aarch64/aarch64-protos.h (aarch64_simd_disambiguate_copy):
 	Declare.