openpower: op-apps: Remove obmc-phosphor-license

This class is on its way to being deprecated, and oe-core packagegroups
don't have a LICENSE specified in the recipe.  Adopt the same semantics
for meta-openpower.

(From meta-openpower rev: 55426381f1e2ad1aeae17f78f29eecee3e4bb1b5)

Change-Id: Icb62e74915ac478b74776299cc1d9ad352accfe6
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>