Makefile: drop unused SRCDIR
Makefile: drop unused SRCDIR

It was unused and srcdir is provided in the environment by default from
autotools.

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

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