drm: exynos: dsi: Add host helper for te_irq_handler

IRQ handler for te-gpio seems to be common across DSIM host.

However, Exynos is handling this via CRTC drivers but there is no clear
evidence on how the same has been handled in i.MX8MM. Keeping the handler
as-it-is can be a viable option but adding DSIM bridge core in upcoming
patches is not possible to call Exynos CRTC handler as DSIM bridge has
to be common across DRM bridge core instead of platform specific DRM
drivers like Exynos here.

So, this patch handles the handler via platform host helper, so-that
handling platform specific hook across Exynos and generic can be
reasonable till it makes it generic across all platforms.

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>