tzdata: reinstate changes reverted in 2014c upgrade

OE-Core commit 57af3fb9 upgraded tzdata
but also reverted a couple of changes to SUMMARY and LIC_FILES_CHKSUM.
Reinstate these (with an update to the README md5 value since that has
changed slightly, without any change to the licensing statements
within).

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>