PEL: Update serverFWRelVer in ext user header section
PEL: Update serverFWRelVer in ext user header section

The Extended User Header section has a field for server
firmware version. Get this field updated from os-release.

Test: Verified PEL tool output for ext user header section

Signed-off-by: Sumit Kumar <ff5b4540db53296dde98178f6d336c6b609ba803@in.ibm.com>
Change-Id: I24cf7a44d71f8afaac3f1d1073fe2a5e13d46628

openbmc/phosphor-logging,openbmc/phosphor-logging,openbmc/phosphor-logging,openbmc/phosphor-logging