x86/ioapic: Correct the PCI/ISA trigger type selection

PCI's default trigger type is level and ISA's is edge. The recent
refactoring made it the other way round, which went unnoticed as it seems
only to cause havoc on some AMD systems.

Make the comment and code do the right thing again.

Fixes: a27dca64 ("x86/io_apic: Cleanup trigger/polarity helpers")
Reported-by: Tom Lendacky <thomas.lendacky@amd.com>
Reported-by: Borislav Petkov <bp@alien8.de>
Reported-by: Qian Cai <cai@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Link: https://lore.kernel.org/r/87d00lgu13.fsf@nanos.tec.linutronix.de