firmware: arm_scmi: Add devm_protocol_acquire helper

Add a method to get hold of a protocol, causing it to be initialized and
its resource accounting updated, without getting access to its operations
and handle.

Some protocols, like SCMI SystemPower, do not expose any protocol ops to
the kernel OSPM agent but still need to be at least initialized. This
helper avoids the need to invoke a full devm_get_protocol() only to get
the protocol initialized while throwing away unused the protocol ops and
handle.

Link: https://lore.kernel.org/r/20220704101933.2981635-4-cristian.marussi@arm.com


Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>