libteec: pkgconfig: rename libteec.pc as teec.pc

Switch naming convention of the pkgconfig metadata file use the plain
namespec without the lib prefix.

While both forms are permitted, the man page of pkg-config[1] has more
examples of metadata files without a lib prefix. Similarly the uuid
metadata file that teeacl uses to link is named simply `uuid.pc`.
Additionally the lib prefix does not provide extra information, and
long lists of pkgconfig metadata files are easier to read with just the
plain namespec.

[1]: https://linux.die.net/man/1/pkg-config



Signed-off-by: Eero Aaltonen <eero.aaltonen@vaisala.com>
Acked-by: Jerome Forissier <jerome.forissier@linaro.org>
Acked-by: Etienne Carriere <etienne.carriere@foss.st.com>