[ot] hw/opentitan: ot_pwrmgr: Fix incorrect WAKE_INFO REASONS field length

(cherry picked from commit 66e7556)

Author: AlexJones0

hw/opentitan/ot_pwrmgr.c

@@ -89,7 +89,7 @@ REG32(ESCALATE_RESET_STATUS, 0x34u)
 REG32(WAKE_INFO_CAPTURE_DIS, 0x38u)
     FIELD(WAKE_INFO_CAPTURE_DIS, VAL, 0u, 1u)
 REG32(WAKE_INFO, 0x3cu)
-    FIELD(WAKE_INFO, REASONS, 0u, 5u)
+    FIELD(WAKE_INFO, REASONS, 0u, 6u)
     FIELD(WAKE_INFO, FALL_THROUGH, 6u, 1u)
     FIELD(WAKE_INFO, ABORT, 7u, 1u)
 REG32(FAULT_STATUS, 0x40u)