libtinyxml2: update to 7.0.1

Backport meta-openembedded libtinyxml2 commits:
  5a0e681262 libtinyxml2: update to 6.2.0
  3e59433d89 libtinyxml2: update to 7.0.1

Yocto 2.6 moves to libtinyxml2 6.2.0 which has a build bug that prevents
bmcweb from building.  Jump ahead to 7.0.1 which has a fix.

Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
Change-Id: I3b97c2df2afe44a88f174a12acbbd110b568a7b7