src/shared/dissect-image.c: fix build without blkdid (#16901)

N_DEVICE_NODE_LIST_ATTEMPTS is unconditionally used since version 246 and
https://github.com/systemd/systemd/commit/ac1f3ad05f7476ae58981dcba45dfeb2c0006824

However, this variable is only defined if HAVE_BLKID is set resulting in
the following build failure if cryptsetup is enabled but not libblkid:

../src/shared/dissect-image.c:1336:34: error: 'N_DEVICE_NODE_LIST_ATTEMPTS' undeclared (first use in this function)
 1336 |         for (unsigned i = 0; i < N_DEVICE_NODE_LIST_ATTEMPTS; i++) {
      |

Fixes:
 - http://autobuild.buildroot.org/results/67782c225c08387c1bbcbea9eee3ca12bc6577cd

src/shared/dissect-image.c

@@ -54,6 +54,9 @@
 #include "user-util.h"
 #include "xattr-util.h"
 
+/* how many times to wait for the device nodes to appear */
+#define N_DEVICE_NODE_LIST_ATTEMPTS 10
+
 int probe_filesystem(const char *node, char **ret_fstype) {
         /* Try to find device content type and return it in *ret_fstype. If nothing is found,
          * 0/NULL will be returned. -EUCLEAN will be returned for ambiguous results, and an
@@ -154,9 +157,6 @@ static int enumerator_for_parent(sd_device *d, sd_device_enumerator **ret) {
         return 0;
 }
 
-/* how many times to wait for the device nodes to appear */
-#define N_DEVICE_NODE_LIST_ATTEMPTS 10
-
 static int wait_for_partitions_to_appear(
                 int fd,
                 sd_device *d,