bufio: removed dead code

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/3779043

src/pkg/bufio/bufio.go

diff --git a/src/pkg/bufio/bufio.go b/src/pkg/bufio/bufio.go
index fc4127a..c13456a 100644
--- a/src/pkg/bufio/bufio.go
+++ b/src/pkg/bufio/bufio.go
@@ -148,7 +148,6 @@
 				b.lastByte = int(p[n-1])
 				b.lastRuneSize = -1
 			}
-			p = p[n:]
 			return n, b.err
 		}
 		b.fill()
@@ -161,7 +160,6 @@
 		n = b.w - b.r
 	}
 	copy(p[0:n], b.buf[b.r:])
-	p = p[n:]
 	b.r += n
 	b.lastByte = int(b.buf[b.r-1])
 	b.lastRuneSize = -1