Fix nanopb python dependencies

The nanopb requirements file did not capture the exact version of the
"protobuf" package. As a result newer version were installed
and that made the build fail.
This fix adds the nanopb package and the proper version to
requirements.txt.

Change-Id: I0e0ad7615828a6fea9fa354623e3b82c560c360d
Signed-off-by: Gyorgy Szing <Gyorgy.Szing@arm.com>
1 file changed