intel/sandybridge: make sure to stay in HLT until reboot

It also tells the compiler that we never leave here.

Change-Id: I824569efd46b577588387b29fc7781abf8c42385
Found-by: Coverity Scan
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/7579
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>

src/northbridge/intel/sandybridge/raminit_native.c

@@ -3751,8 +3751,10 @@ void init_dram_ddr3(spd_raw_data * spds, int mobile, int min_tck,
 		if (!mrc_cache || mrc_cache->mrc_data_size < sizeof (ctrl)) {
 			/* Failed S3 resume, reset to come up cleanly */
 			outb(0x6, 0xcf9);
+			while (1) {
 				hlt();
 			}
+		}
 		memcpy(&ctrl, mrc_cache->mrc_data, sizeof (ctrl));
 	}