drm/i915/uncore: cast iomem to avoid sparse warning

drmm_add_action_or_reset() is unaware of __iomem and the pointer needs
to be a plain void *. Cast __iomem away and back while the pointer goes
through drmm.

drivers/gpu/drm/i915/intel_uncore.c:2463:17: warning: incorrect type in argument 1 (different address spaces)
drivers/gpu/drm/i915/intel_uncore.c:2463:17:    expected void volatile [noderef] __iomem *addr
drivers/gpu/drm/i915/intel_uncore.c:2463:17:    got void *regs
drivers/gpu/drm/i915/intel_uncore.c:2494:16: warning: incorrect type in argument 3 (different address spaces)
drivers/gpu/drm/i915/intel_uncore.c:2494:16:    expected void *data
drivers/gpu/drm/i915/intel_uncore.c:2494:16:    got void [noderef] __iomem *regs

Cc: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230207124026.2105442-2-jani.nikula@intel.com