cpu/x86/lapic: Support x86_64 and clean up code

Most LAPIC registers are 32bit, and thus the use of long is valid on
x86_32, however it doesn't work on x86_64.

* Don't use long as it is 64bit on x86_64, which breaks interrupts
  in QEMU and thus SeaBIOS wouldn't time out the boot menu
* Get rid of unused defines
* Get rid of unused atomic xchg code

Tested on QEMU Q35 with x86_64 enabled: Interrupts work again.
Tested on QEMU Q35 with x86_32 enabled: Interrupts are still working.
Tested on Lenovo T410 with x86_64 enabled.

Change-Id: Iaed1ad956d090625c7bb5cd9cf55cbae16dd82bd
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36777
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/cpu/x86/lapic/lapic.c

@@ -47,6 +47,6 @@ void do_lapic_init(void)
 			LAPIC_DELIVERY_MODE_NMI)
 		);
 
-	printk(BIOS_DEBUG, " apic_id: 0x%02lx ", lapicid());
+	printk(BIOS_DEBUG, " apic_id: 0x%02x ", lapicid());
 	printk(BIOS_INFO, "done.\n");
 }