Kernel/FileSystem: Don't assume flags for root filesystem mount flags

This is considered somewhat an abstraction layer violation, because we
should always let userspace to decide on the root filesystem mount flags
because it allows the user to configure the mount table to preferences
that they desire.
Now that SystemServer is modified to re-mount the root mount with the
desired flags, we can just mount the root filesystem without assuming
special flags.

Kernel/FileSystem/VirtualFileSystem.cpp

@@ -26,7 +26,7 @@
 namespace Kernel {
 
 static Singleton<VirtualFileSystem> s_the;
-static constexpr int root_mount_flags = MS_NODEV | MS_NOSUID | MS_RDONLY;
+static constexpr int root_mount_flags = 0;
 
 UNMAP_AFTER_INIT void VirtualFileSystem::initialize()
 {