mhi: core: Disable preemption while processing data events

If data processing of an event is scheduled out because core
is busy handling multiple irqs, this can starves the processing
of MHI M0 state change event on another core. Fix this issue by
disabling irq on the core processing data events.

Change-Id: I4d784d2c343d4a9c50741f3e72df4c373993ae79
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>