ACPI: Move PICM declaration

Variable PICM was not inside GNVS region and can use a static
initialisation value.

For most AMD platforms PICM default changes from 1 to 0.

Fix comments about PICM==0 used to indicate use of i8259 PIC for
interrupt delivery.

Change-Id: I525ef8353514ec32941c4d0c37cab38aa320cb20
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/49905
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/lippert/frontrunner-af/dsdt.asl

@@ -38,7 +38,6 @@ DefinitionBlock (
 	/* Some global data */
 	Name(OSVR, 3)		/* Assume nothing. WinXp = 1, Vista = 2, Linux = 3, WinCE = 4 */
 	Name(OSV, Ones)	/* Assume nothing */
-	Name(PICM, One)	/* Assume APIC */
 
 	/*
 	 * Processor Object