bus: mhi: ep: Do not allocate event ring element on stack

bus: mhi: ep: Do not allocate event ring element on stack

[ Upstream commit 987fdb5a43a66764808371b54e6047834170d565 ]

It is possible that the host controller driver would use DMA framework to
write the event ring element. So avoid allocating event ring element on the
stack as DMA cannot work on vmalloc memory.

Cc: stable@vger.kernel.org
Fixes: 961aeb689224 ("bus: mhi: ep: Add support for sending events to the host")
Link: https://lore.kernel.org/r/20230901073502.69385-1-manivannan.sadhasivam@linaro.org
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Stable-dep-of: 327ec5f70609 ("PCI: epf-mhi: Fix the DMA data direction of dma_unmap_single()")
Signed-off-by: Sasha Levin <sashal@kernel.org>