[POWERPC] IOMMU virtual merge is no longer experimental

Per conversations with BenH, IOMMU virtual merging should no longer
be considered to be an "experimental" feature.  In particular,
CONFIG_VMERGE has been set to "y" in the defconfigs for quite a while.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

----
 arch/powerpc/Kconfig |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)
Signed-off-by: Paul Mackerras <paulus@samba.org>