x86: irq_remapping: Move irq remapping mode enum

The enum is currently defined in Intel-specific DMAR header file,
but it is also used by APIC common code. Therefore, move it to
a more appropriate interrupt-remapping common header file.
This will also be used by subsequent patches.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>