docbook: fix fatal error from libata

docbook: fix fatal error from libata

'make htmldocs' has a fatal error when processing libata.xml, as seen
below.  The string "Example patterns:" (or any string with "example.*:"
in it AFAIK) causes some part of the doc generation tool chain to try to
produce an <informalexample> block without a beginning <para>, but
there is an ending </para> generated, which throws things out of kilter.

I don't even know where (what program) this is happening in.
I searched in docproc and xmlto and in some XML stylesheets without
finding anything.  If anyone can give me pointers about this, please do.
Until this is fixed, let's just spell "Example" as "Sample"
and match up the double quotation marks while there.

  Documentation/DocBook/libata.xml:6575: parser error : Opening and ending tag mismatch: programlisting line 6573 and para
     </para><para>
            ^
  Documentation/DocBook/libata.xml:6580: parser error : Opening and ending tag mismatch: para line 6575 and programlisting
  </programlisting></informalexample>
                   ^
  unable to parse Documentation/DocBook/libata.xml
  make[2]: *** [Documentation/DocBook/libata.html] Error 1

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>