drivers/mrc_cache: Make bootstate for SPI writes variable

The default time for writing MRC data to flash is at the exit of
BS_DEV_ENUMERATE but this is too early for some implementations.
Add an option to Kconfig for allowing a late option to be selected.
The timing of the late option is at the entry of BS_OS_RESUME_CHECK.

TEST=Select option and inspect console log on Kahlee
BUG=b:69614064

Change-Id: Ie7ba9070829d98414ee788e14d1a768145d742ea
Signed-off-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-on: https://review.coreboot.org/22937
Reviewed-by: Martin Roth <martinroth@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/drivers/mrc_cache/mrc_cache.c

@@ -574,8 +574,12 @@ static void update_mrc_cache(void *unused)
 }
 
 /*
- * Ensures MRC training data is stored into SPI after PCI enumeration is done
- * during BS_DEV_ENUMERATE-BS_ON_EXIT and lock down SPI protected ranges
- * during BS_DEV_RESOURCES-BS_ON_EXIT.
+ * Ensures MRC training data is stored into SPI after PCI enumeration is done.
+ * Some implementations may require this to be later than others.
  */
+
+#if IS_ENABLED(CONFIG_MRC_WRITE_NV_LATE)
+BOOT_STATE_INIT_ENTRY(BS_OS_RESUME_CHECK, BS_ON_ENTRY, update_mrc_cache, NULL);
+#else
 BOOT_STATE_INIT_ENTRY(BS_DEV_ENUMERATE, BS_ON_EXIT, update_mrc_cache, NULL);
+#endif