doc/asm: fix HTML markup

Change-Id: I33bde4835d3b83fafd55beea483f6236c4c62840
Reviewed-on: https://go-review.googlesource.com/c/go/+/338990
Reviewed-by: Ian Lance Taylor <[email protected]>
Trust: Than McIntosh <[email protected]>

Author: xen0n

doc/asm.html

@@ -125,8 +125,8 @@ <h3 id="constants">Constants</h3>
 One is in constant evaluation.
 Constant expressions in the assembler are parsed using Go's operator
 precedence, not the C-like precedence of the original.
-Thus <code>3&amp;1<<2</code> is 4, not 0—it parses as <code>(3&amp;1)<<2</code>
-not <code>3&amp;(1<<2)</code>.
+Thus <code>3&amp;1&lt;&lt;2</code> is 4, not 0—it parses as <code>(3&amp;1)&lt;&lt;2</code>
+not <code>3&amp;(1&lt;&lt;2)</code>.
 Also, constants are always evaluated as 64-bit unsigned integers.
 Thus <code>-2</code> is not the integer value minus two,
 but the unsigned 64-bit integer with the same bit pattern.
@@ -914,8 +914,6 @@ <h3 id="ppc64">PPC64</h3>
 Reference: <a href="/pkg/cmd/internal/obj/ppc64">Go PPC64 Assembly Instructions Reference Manual</a>
 </p>
 
-</ul>
-
 <h3 id="s390x">IBM z/Architecture, a.k.a. s390x</h3>
 
 <p>