soc/amd/common/block/acpi/pm_state: don't rely on undefined behavior

Change-Id: I5a76a38f8d84666f6b9c0bfffecca064fa82d593
Found-by: Coverity CID 1445994
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50492
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>

src/soc/amd/common/block/acpi/pm_state.c

@@ -18,7 +18,7 @@ static int get_index_bit(uint32_t value, uint16_t limit)
 		return -1;
 
 	/* get a mask of valid bits. Ex limit = 3, set bits 0-2 */
-	t = (1 << limit) - 1;
+	t = (1ULL << limit) - 1;
 	if ((value & t) == 0)
 		return -1;
 	t = 1;