[MIPS] iounmap if in vr41xx_pciu_init() pci clock is over 33MHz

iounmap if pci clock is over 33MHz.  Cosmetic because the iomap() in this
case is just a bit of address magic.

Signed-off-by: Roel Kluin <12o3l@tiscali.nl>
Acked-by: Yoichi Yuasa <yoichi_yuasa@tripeaks.co.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>