runtime: remove indentation in mapiternext

Invert the condition and continue, to remove indentation.

Change-Id: Id62a5d9abc9a4df1193bcf15f95f70f2c2e2abac
Reviewed-on: https://go-review.googlesource.com/55091
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Martin Möhrmann <moehrmann@google.com>

src/runtime/hashmap.go

@@ -820,7 +820,9 @@ next:
 		offi := (i + it.offset) & (bucketCnt - 1)
 		k := add(unsafe.Pointer(b), dataOffset+uintptr(offi)*uintptr(t.keysize))
 		v := add(unsafe.Pointer(b), dataOffset+bucketCnt*uintptr(t.keysize)+uintptr(offi)*uintptr(t.valuesize))
-		if b.tophash[offi] != empty && b.tophash[offi] != evacuatedEmpty {
+		if b.tophash[offi] == empty || b.tophash[offi] == evacuatedEmpty {
+			continue
+		}
 		if checkBucket != noCheck && !h.sameSizeGrow() {
 			// Special case: iterator was started during a grow to a larger size
 			// and the grow is not done yet. We're working on a bucket whose
@@ -902,7 +904,6 @@ next:
 		it.checkBucket = checkBucket
 		return
 	}
-	}
 	b = b.overflow(t)
 	i = 0
 	goto next