drm/msm/dsi: Remove spurious IRQF_ONESHOT flag

drm/msm/dsi: Remove spurious IRQF_ONESHOT flag

BugLink: https://bugs.launchpad.net/bugs/1969107
[ Upstream commit 24b176d8827d167ac3b379317f60c0985f6e95aa ]

Quoting the header comments, IRQF_ONESHOT is "Used by threaded interrupts
which need to keep the irq line disabled until the threaded handler has
been run.". When applied to an interrupt that doesn't request a threaded
irq then IRQF_ONESHOT has a lesser known (undocumented?) side effect,
which it to disable the forced threading of irqs (and for "normal" kernels
it is a nop). In this case I can find no evidence that suppressing forced
threading is intentional. Had it been intentional then a driver must adopt
the raw_spinlock API in order to avoid deadlocks on PREEMPT_RT kernels
(and avoid calling any kernel API that uses regular spinlocks).

Fix this by removing the spurious additional flag.

This change is required for my Snapdragon 7cx Gen2 tablet to boot-to-GUI
with PREEMPT_RT enabled.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20220201174734.196718-2-daniel.thompson@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit e45d1d19a0bb29f6454e2fa87559325d62538f5f)
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>