basic/errno-list: remove errno_max() and define ERRNO_MAX as 4095

In Linux kernel code, MAX_ERRNO is defined as 4095.
Here, we use that value for ERRNO_MAX.

src/basic/errno-list.c

@@ -51,7 +51,3 @@ int errno_from_name(const char *name) {
         assert(sc->id > 0);
         return sc->id;
 }
-
-int errno_max(void) {
-        return ELEMENTSOF(errno_names);
-}

src/basic/errno-list.h

@@ -19,7 +19,11 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+/*
+ * MAX_ERRNO is defined as 4095 in linux/err.h
+ * We use the same value here.
+ */
+#define ERRNO_MAX 4095
+
 const char *errno_to_name(int id);
 int errno_from_name(const char *name);
-
-int errno_max(void);