bus: mhi: fix typo in comments for struct mhi_channel_config

The word 'rung' is a typo in below comment, fix it.
* @event_ring: The event rung index that services this channel

Signed-off-by: Jarvis Jiang <jarvis.w.jiang@gmail.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20210408100220.3853-1-jarvis.w.jiang@gmail.com


Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>