cpu/x86/mp_init: use cb_err as mp_init_with_smm return type

Using cb_err as return type clarifies the meaning of the different
return values. This patch also adds the types.h include that provides
the definition of the cb_err enum and checks the return value of
mp_init_with_smm against the enum values instead of either checking if
it's non-zero or less than zero to handle the error case.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: Ibcd4a9a63cc87fe176ba885ced0f00832587d492
Reviewed-on: https://review.coreboot.org/c/coreboot/+/58491
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>

src/mainboard/emulation/qemu-i440fx/northbridge.c

@@ -13,6 +13,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <smbios.h>
+#include <types.h>
 #include "memory.h"
 
 #include "fw_cfg.h"
@@ -250,7 +251,7 @@ void mp_init_cpus(struct bus *cpu_bus)
 {
 	const struct mp_ops *ops = CONFIG(SMM_TSEG) ? &mp_ops_with_smm : &mp_ops_no_smm;
 
-	if (mp_init_with_smm(cpu_bus, ops))
+	if (mp_init_with_smm(cpu_bus, ops) != CB_SUCCESS)
 		printk(BIOS_ERR, "MP initialization failure.\n");
 }