read pcr: Change output format to be more readable
read pcr: Change output format to be more readable

PCR values are usually reffered to with hex values, so this
increases usablity.

Signed-off-by: Joe Richey <24d3dd8348b5cac19a417e52b4f8141ba91506f0@google.com>

google/go-tpm-tools,google/go-tpm-tools,google/go-tpm-tools