libpfdi: Add PFDI user-space library

This commit introduces libpfdi, a library that facilitates interaction
between user applications and the Linux device driver for platform
fault detection Interface.

It provides public APIs that allow user applications to invoke PFDI
functionalities.

Signed-off-by: Ziad Elhanafy <ziad.elhanafy@arm.com>
Signed-off-by: Divin Raj <divin.raj@arm.com>