dt-bindings: mailbox: Add compatible for SM8350 IPCC

Add the compatible string for SM8350 IPCC block on this SoC

Signed-off-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>