files: check fseek return value
files: check fseek return value

If fseek fails we ignore it, and the file won't be in the expected
state. Cause the check to fail and print a message.

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

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