tpm2_nvreadpublic: use getcap helper in tpm2.c
tpm2_nvreadpublic: use getcap helper in tpm2.c

Progresses: #1520
Progresses: #1539

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

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