BUILD: stick-table: fix build error on 32-bit platforms

Commit 9b2717e ("MINOR: stktable: use {show,set,clear} table with ptr")
stores a pointer in a long long (64bit), which fails the cas to void* on
32-bit platforms:

  src/stick_table.c: In function 'table_process_entry_per_ptr':
  src/stick_table.c:5136:37: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
   5136 |         ts = stktable_lookup_ptr(t, (void *)ptr);

On all our supported platforms, longs and pointers are of the same size,
so let's just turn this to a ulong instead.

src/stick_table.c

@@ -5121,15 +5121,15 @@ static int table_process_entry_per_ptr(struct appctx *appctx, char **args)
 {
 	struct show_table_ctx *ctx = appctx->svcctx;
 	struct stktable *t = ctx->target;
-	long long int ptr;
+	ulong ptr;
 	char *error;
 	struct stksess *ts;
 
 	if (!*args[4] || args[4][0] != '0' || args[4][1] != 'x')
 		return cli_err(appctx, "Pointer expected (0xffff notation)\n");
 
 	/* Convert argument to integer value */
-	ptr = strtoll(args[4], &error, 16);
+	ptr = strtoul(args[4], &error, 16);
 	if (*error != '\0')
 		return cli_err(appctx, "Malformed ptr.\n");