kernel/vm: Add some more AssertLocked()s in VMCache commitment methods.

And remove a now-redundant one.

src/system/kernel/vm/VMAnonymousCache.cpp

@@ -720,6 +720,8 @@ VMAnonymousCache::Commit(off_t size, int priority)
 {
 	TRACE("%p->VMAnonymousCache::Commit(%" B_PRIdOFF ")\n", this, size);
 
+	AssertLocked();
+
 	// If we can overcommit, we don't commit here, but in Fault(). We always
 	// unreserve memory, if we're asked to shrink our commitment, though.
 	if (fCanOvercommit && size > committed_size) {

src/system/kernel/vm/VMAnonymousNoSwapCache.cpp

@@ -61,6 +61,8 @@ VMAnonymousNoSwapCache::Init(bool canOvercommit, int32 numPrecommittedPages,
 status_t
 VMAnonymousNoSwapCache::Commit(off_t size, int priority)
 {
+	AssertLocked();
+
 	// If we can overcommit, we don't commit here, but in Fault(). We always
 	// unreserve memory, if we're asked to shrink our commitment, though.
 	if (fCanOvercommit && size > committed_size) {

src/system/kernel/vm/VMCache.cpp

@@ -1083,8 +1083,6 @@ VMCache::SetMinimalCommitment(off_t commitment, int priority)
 {
 	TRACE(("VMCache::SetMinimalCommitment(cache %p, commitment %" B_PRIdOFF
 		")\n", this, commitment));
-	AssertLocked();
-
 	T(SetMinimalCommitment(this, commitment));
 
 	status_t status = B_OK;