OvmfPkg/VirtioFsDxe: implement the wrapper function for FUSE_FORGET

Add the VirtioFsFuseForget() function, for sending the FUSE_FORGET command
to the Virtio Filesystem device.

This is an unusual command in that it doesn't generate any response from
the FUSE server.

Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3097
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20201216211125.19496-13-lersek@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@arm.com>

OvmfPkg/VirtioFsDxe/VirtioFsDxe.inf

@@ -82,6 +82,7 @@
 
 [Sources]
   DriverBinding.c
+  FuseForget.c
   FuseInit.c
   FuseOpenDir.c
   FuseRelease.c