drm/i915/irq: split out display irq handling

Split (non-hotplug) display irq handling out of i915_irq.[ch] into
display/intel_display_irq.[ch].

v3:
- Preserve [I915_MAX_PIPES] harder (kernel test robot)

v2:
- Rebase
- Preserve [I915_MAX_PIPES] in functions (kernel test robot)

Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230515101738.2399816-3-jani.nikula@intel.com