netcat: add from OE-Classic

Changes from the OE-Classic recipe:
* Use ALTERNATIVE_${PN} instead of ALTERNATIVE_NAME
* Add LIC_FILES_CHKSUM
* Move SRC_URI checksums underneath SRC_URI

Based on a patch by Vladimir Redzhepoff <vladimir.redzhepoff@promwad.com>

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