feat: added not implemented function

kernel/libk/libk.c

@@ -21,6 +21,10 @@ void att_noreturn k_panics(const char *msg) {
     k_panic();
 }
 
+void att_noreturn k_not_implemented()  {
+    k_panics("Not Implemented");
+}
+
 void att_noreturn k_panic() {
     kprint_sync("PANIC!");
     while (1) {

kernel/vfs/lfs/ext2.c

@@ -141,7 +141,7 @@ int ext2_get_block_from_inode(vfs_mount_t *mount, vfs_fd_t *fd, void *target, ui
         }
         return ext2_read_blocks(mount, bp, 1, target);
     } else {
-        k_panics("Not implemented");
+        k_not_implemented();
     }
 }