machine: use size_t for array sizes (#10309)

Some uses of n_netif already assumed it had time size_t. Others were a
bit sloppy. Let's clean this up.

src/machine/machine.c

@@ -183,7 +183,7 @@ int machine_save(Machine *m) {
                         m->timestamp.monotonic);
 
         if (m->n_netif > 0) {
-                unsigned i;
+                size_t i;
 
                 fputs("NETIF=", f);
 

src/machine/machine.h

@@ -57,7 +57,7 @@ struct Machine {
         sd_bus_message *create_message;
 
         int *netif;
-        unsigned n_netif;
+        size_t n_netif;
 
         LIST_HEAD(Operation, operations);
 

src/machine/machinectl.c

@@ -540,7 +540,7 @@ typedef struct MachineStatusInfo {
         pid_t leader;
         struct dual_timestamp timestamp;
         int *netif;
-        unsigned n_netif;
+        size_t n_netif;
 } MachineStatusInfo;
 
 static void machine_status_info_clear(MachineStatusInfo *info) {
@@ -600,7 +600,7 @@ static void print_machine_status_info(sd_bus *bus, MachineStatusInfo *i) {
                 printf("\t    Root: %s\n", i->root_directory);
 
         if (i->n_netif > 0) {
-                unsigned c;
+                size_t c;
 
                 fputs("\t   Iface:", stdout);