drm/i915/audio: drop irq enabled check from LPE audio setup

drm/i915/audio: drop irq enabled check from LPE audio setup

There shouldn't be anything requiring irqs to be enabled at the point of
LPE audio setup. Regardless, we've never hit the warning, as irqs are
always enabled at the time LPE audio is initialized. Drop the
superfluous warning, and the dependency on i915_drv.h.

Fix style a bit while at it.

Reviewed-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
Link: https://lore.kernel.org/r/20250801122832.249985-1-jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>