tpm2_create: fix -I - option argument
tpm2_create: fix -I - option argument

A regression was introduced that caused -I - to report that file "-"
does not exist. This is because the check for "-" was removed, and
that indicates that stdin should be used. When "-" is used, set
the path to NULL so the load routine grabs from stdin and not
path "-".

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

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