doc/go1.7.html: remove erroneous note about ppc64 and power8

We decided that ppc64 should maintain power5 compatibility.
ppc64le requires power8.

Fixes #16372.

Change-Id: If5b309a0563f55a3c1fe9c853d29a463f5b71101
Reviewed-on: https://go-review.googlesource.com/24915Reviewed-by: Minux Ma <minux@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

doc/go1.7.html

@@ -91,8 +91,10 @@ added in Go 1.6 now have full support for cgo and external linking.
 </p>
 
 <p>
-The experimental port to Linux on big-endian 64-bit PowerPC (<code>linux/ppc64</code>)
+The experimental port to Linux on little-endian 64-bit PowerPC (<code>linux/ppc64le</code>)
 now requires the POWER8 architecture or later.
+Big-endian 64-bit PowerPC (<code>linux/ppc64</code>) only requires the
+POWER5 architecture.
 </p>
 
 <p>