drm/tidss: IRQ code cleanup

The IRQ setup code is overly complex. All we really need to do is
initialize the related fields in struct tidss_device, and request the
IRQ.

We can drop all the HW accesses, as they are pointless: the driver will
set the IRQs correctly when it needs any of the IRQs, and at probe time
we have done a reset, so we know that all the IRQs are masked by default
in the hardware.

Thus we can combine the tidss_irq_preinstall() and
tidss_irq_postinstall() into the tidss_irq_install() function, drop the
HW accesses, and drop the use of spinlock, as this is done at init time
and there can be no races.

We can also drop the HW access from the tidss_irq_uninstall(), as the
driver will anyway disable and suspend the hardware at remove time.

Reviewed-by: Aradhya Bhatia <a-bhatia1@ti.com>
Link: https://lore.kernel.org/r/20231109-tidss-probe-v2-9-ac91b5ea35c0@ideasonboard.com


Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>