Plus naming convention for runtime pm tests to have "rpm" somewhere in
their tests. Note that all the pc8-specific tests (for e.g. residency
or similar) already have pc8 in their subtest names, so we don't lose
any information here.

Cc: "Yang, Guang A" <guang.a.yang@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>