AArch64: Fix printf format strings.

Use the portable printf format strings as defined in:

http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml#64-bit_Portability



These changes are necessary when compiling for LP64 architectures.

Change-Id: I3ff355dda5a7a72a8e659a7e5d2014aa4e62f8c3
Signed-off-by: Matthew Leach <matthew.leach@arm.com>
Signed-off-by: Matteo Franchin <matteo.franchin@arm.com>