libvpd: Update outdated README file
libvpd: Update outdated README file

Current README file is outdated and doesn't contain all required
information. Here is an attempt to update README file with relevant
information.

Signed-off-by: Vasant Hegde <a6d753843573f7bfed5075c1e875b0be8007a0ab@linux.vnet.ibm.com>

kamalesh-babulal/libvpd,kamalesh-babulal/libvpd,kamalesh-babulal/libvpd