bus: mhi: host: Rename "struct mhi_tre" to "struct mhi_ring_element"

Structure "struct mhi_tre" is representing a generic MHI ring element and
not specifically a Transfer Ring Element (TRE). Fix the naming.

Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20220301160308.107452-9-manivannan.sadhasivam@linaro.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>