firmware: arm_scmi: Drop checking for shmem property in parent node

The scmi protocol core driver checks for the channel availability
before evaluating the shmem property. If the individual protocols
don't have separate channel assigned to them, the channel alloted
for the BASE protocol is reused automatically.

Therefore there is no need to check for the shmem property in the
parent node if it is absent in the child protocol node.

Link: https://lore.kernel.org/r/20200327163654.13389-5-sudeep.holla@arm.com


Tested-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>