[FASTFAT] Drop read ahead locking routines in favor of lazy writer routines.

This avoids code duplication while being consistent with MS FastFAT.

drivers/filesystems/fastfat/fastio.c

@@ -753,36 +753,6 @@ VfatReleaseFromLazyWrite(
     ExReleaseResourceLite(&(Fcb->MainResource));
 }
 
-BOOLEAN
-NTAPI
-VfatAcquireForReadAhead(
-    IN PVOID Context,
-    IN BOOLEAN Wait)
-{
-    PVFATFCB Fcb = (PVFATFCB)Context;
-    ASSERT(Fcb);
-    DPRINT("VfatAcquireForReadAhead(): Fcb %p\n", Fcb);
-
-    if (!ExAcquireResourceExclusiveLite(&(Fcb->MainResource), Wait))
-    {
-        DPRINT("VfatAcquireForReadAhead(): ExReleaseResourceLite failed.\n");
-        return FALSE;
-    }
-    return TRUE;
-}
-
-VOID
-NTAPI
-VfatReleaseFromReadAhead(
-    IN PVOID Context)
-{
-    PVFATFCB Fcb = (PVFATFCB)Context;
-    ASSERT(Fcb);
-    DPRINT("VfatReleaseFromReadAhead(): Fcb %p\n", Fcb);
-
-    ExReleaseResourceLite(&(Fcb->MainResource));
-}
-
 INIT_SECTION
 VOID
 VfatInitFastIoRoutines(

drivers/filesystems/fastfat/iface.c

@@ -119,8 +119,8 @@ DriverEntry(
     /* Cache manager */
     VfatGlobalData->CacheMgrCallbacks.AcquireForLazyWrite = VfatAcquireForLazyWrite;
     VfatGlobalData->CacheMgrCallbacks.ReleaseFromLazyWrite = VfatReleaseFromLazyWrite;
-    VfatGlobalData->CacheMgrCallbacks.AcquireForReadAhead = VfatAcquireForReadAhead;
+    VfatGlobalData->CacheMgrCallbacks.AcquireForReadAhead = VfatAcquireForLazyWrite;
-    VfatGlobalData->CacheMgrCallbacks.ReleaseFromReadAhead = VfatReleaseFromReadAhead;
+    VfatGlobalData->CacheMgrCallbacks.ReleaseFromReadAhead = VfatReleaseFromLazyWrite;
 
     /* Fast I/O */
     VfatInitFastIoRoutines(&VfatGlobalData->FastIoDispatch);

drivers/filesystems/fastfat/vfat.h

@@ -775,17 +775,6 @@ NTAPI
 VfatReleaseFromLazyWrite(
     IN PVOID Context);
 
-BOOLEAN
-NTAPI
-VfatAcquireForReadAhead(
-    IN PVOID Context,
-    IN BOOLEAN Wait);
-
-VOID
-NTAPI
-VfatReleaseFromReadAhead(
-    IN PVOID Context);
-
 /* fat.c */
 
 NTSTATUS