Kernel & Userland: Allow to mount image files formatted with Ext2FS

Author: https://github.com/supercomputer7
Commit: a60ea79a41
Pull-request: https://github.com/SerenityOS/serenity/pull/1513
Issue: https://github.com/SerenityOS/serenity/issues/1351
Reviewed-by: https://github.com/bugaevc

Libraries/LibC/unistd.cpp

@@ -582,14 +582,15 @@ int reboot()
     __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
-int mount(const char* source, const char* target, const char* fs_type, int flags)
+int mount(int source_fd, const char* target, const char* fs_type, int flags)
 {
-    if (!source || !target || !fs_type) {
+    if (!target || !fs_type) {
         errno = EFAULT;
         return -1;
     }
+
     Syscall::SC_mount_params params {
-        { source, strlen(source) },
+        source_fd,
         { target, strlen(target) },
         { fs_type, strlen(fs_type) },
         flags