json: Update jsmn library to upstream commit 053d3cd

Update our embedded version of the jsmn library to upstream commit
053d3cd (Merge pull request #175 from pks-t/pks/struct-type,
2020-04-02).

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/lib/json/jsmn.h

@@ -66,7 +66,7 @@ enum jsmnerr {
  * start	start position in JSON data string
  * end		end position in JSON data string
  */
-typedef struct {
+typedef struct jsmntok {
   jsmntype_t type;
   int start;
   int end;
@@ -80,7 +80,7 @@ typedef struct {
  * JSON parser. Contains an array of token blocks available. Also stores
  * the string being parsed now and current position in that string.
  */
-typedef struct {
+typedef struct jsmn_parser {
   unsigned int pos;     /* offset in the JSON string */
   unsigned int toknext; /* next token to allocate */
   int toksuper;         /* superior token node, e.g. parent object or array */
@@ -154,6 +154,9 @@ static int jsmn_parse_primitive(jsmn_parser *parser, const char *js,
     case ']':
     case '}':
       goto found;
+    default:
+                   /* to quiet a warning from gcc*/
+      break;
     }
     if (js[parser->pos] < 32 || js[parser->pos] >= 127) {
       parser->pos = start;