linux-user: ppc64: fix ARCH_206 bit in AT_HWCAP

Only the POWER[789] CPUs should have the ARCH_206 bit set. This is what the
linux kernel does. I guess this was also the intention of commit 0e019746.
We have to make sure all *206 bits are set.

Before this patch, the flags check in the GET_FEATURES2 macro returned true
if _any_ bit was set. This worked well as long as there was only one bit
set in the 'flag' parameter. But as explained before, we have to make sure
all bits in the 'flag' parameter are set.

Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>