drivers/macintosh/via-pmu.c: Added a missing iounmap

The error handling code should undo the ioremap as well.

The problem was detected using the following semantic match
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@@
type T,T1,T2;
identifier E;
statement S;
expression x1,x2;
constant C;
int ret;
@@

  T E;
  ...
* E = ioremap(...);
  if (E == NULL) S
  ... when != iounmap(E)
      when != if (E != NULL) { ... iounmap(E); ...}
      when != x1 = (T1)E
  if (...) {
    ... when != iounmap(E)
        when != if (E != NULL) { ... iounmap(E); ...}
        when != x2 = (T2)E
(
*   return;
|
*   return C;
|
*   return ret;
)
  }
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Olaf Hering <olaf@aepfle.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>