[ot] hw/opentitan: ot_rstmgr: Fix incorrect CPU_INFO_CTRL INDEX field location

(cherry picked from commit bdb7b86)

Author: AlexJones0

hw/opentitan/ot_rstmgr.c

@@ -77,7 +77,7 @@ REG32(CPU_REGWEN, 0x1cu)
     FIELD(CPU_REGWEN, EN, 0u, 1u)
 REG32(CPU_INFO_CTRL, 0x20u)
     FIELD(CPU_INFO_CTRL, EN, 0u, 1u)
-    FIELD(CPU_INFO_CTRL, INDEX, 0u, 4u)
+    FIELD(CPU_INFO_CTRL, INDEX, 4u, 4u)
 REG32(CPU_INFO_ATTR, 0x24u)
     FIELD(CPU_INFO_ATTR, CNT_AVAIL, 0u, 4u)
 REG32(CPU_INFO, 0x28u)