iommu/vt-d: Downgrade warning for pre-enabled IR

iommu/vt-d: Downgrade warning for pre-enabled IR

Emitting a warning is overkill in intel_setup_irq_remapping() since the
interrupt remapping is pre-enabled. For example, there's no guarantee
that kexec will explicitly disable interrupt remapping before booting a
new kernel. As a result, users are seeing warning messages like below
when they kexec boot a kernel, though there is nothing wrong:

 DMAR-IR: IRQ remapping was enabled on dmar18 but we are not in kdump mode
 DMAR-IR: IRQ remapping was enabled on dmar17 but we are not in kdump mode
 DMAR-IR: IRQ remapping was enabled on dmar16 but we are not in kdump mode
 ... ...

Downgrade the severity of this message to avoid user confusion.

CC: Paul Menzel <pmenzel@molgen.mpg.de>
Link: https://lore.kernel.org/linux-iommu/5517f76a-94ad-452c-bae6-34ecc0ec4831@molgen.mpg.de/
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20240625043912.258036-1-baolu.lu@linux.intel.com
Link: https://lore.kernel.org/r/20240702130839.108139-5-baolu.lu@linux.intel.com
Signed-off-by: Will Deacon <will@kernel.org>