plugin-api: resourced: Move common struct and enum from *.h to *-interface.h

plugin-api: resourced: Move common struct and enum from *.h to *-interface.h

Move common struct and enum, referened by both resourced and resourced backend,
from syscommon-plugin-resourced-memory-lmk.h
to syscommon-plugin-resourced-memory-lmk-interface.h for consistency.

*.h can be referenced only by resourced. On the other hand, *-interface.h can
be referenced by both side. Therefore, common struct and enum should be
defined in *-interface.h.

Change-Id: I0529e21da6688eeebb9a0583521dc69c2e400f2c
Signed-off-by: Unsung Lee <unsung.lee@samsung.com>