tpm2_getpubak.c: fix casts assume memory size
tpm2_getpubak.c: fix casts assume memory size

Relates to: #228

Signed-off-by: William Roberts <60148e894dabf0b83bde1d460768794cd453c455@intel.com>

01org/tpm2.0-tools,martinezjavier/tpm2-tools,01org/tpm2.0-tools,01org/tpm2.0-tools,martinezjavier/tpm2-tools,martinezjavier/tpm2-tools,martinezjavier/tpm2-tools