arch: Convert formatter strings to use PRI defines

To allow for various libc implementations (like newlib) in which the way
various {u}int{8,16,32}_t types are defined vary between both libc
implementations and across architectures we need to utilize the PRI
defines.

Change-Id: Ic4e65db52c8d693228cf80584283d4d06e68b5ad
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>