drm/i915/irq: move locking inside vlv_display_irq_reset()

All users of vlv_display_irq_reset() have a lock/unlock pair. Move the
locking inside the function.

Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://lore.kernel.org/r/0f8176b777fa24921458996f7d6f982f955a52f6.1746536745.git.jani.nikula@intel.com


Signed-off-by: Jani Nikula <jani.nikula@intel.com>