Add get_local_cpuname to the rpmsg framework ops to support communicate
with the same remote core with multi rpmsg transport.
Some rpmsg services will send local cpu name to remote core and then let
remote core to connect local core by using this cpu name, when there are
multi rpmsg channels with same remote core, the remote core may connect
to incorrect core, so use the error rpmsg channel.
For example, there are two rpmsg channels between ap and audio:
ap core audio core
[ap1] <-- rpmsg virtio1 --> [audio1]
[ap2] <-- rpmsg virtio2 --> [audio2]
When we want to use the rpmsg virtio1 to communicate, ap core may send
local cpuname "ap2" to audio, so the audio core use remote cpu "ap2" to
connect with ap, and resulting in the use of incorrect rpmsg channel.
Signed-off-by: Bowen Wang <wangbowen6@xiaomi.com>