more segment/selector handling woes

["Jan Beulich" <jbeulich@novell.com>]

Not only on VMX and in generic code, but also on SVM now:
svm_get_io_address() uses the segment base only when the guest
is not in long mode - what if outs has an fs/gs override? I'm pretty
sure the base address is needed then, which opens the question -
does the CPU guarantee a valid (zero) base also for the other
segment register, or does this need to be conditionalized?

Further, in the same function (and likely elsewhere) the injection
of GP faults seems pretty pointless - if either of the two
conditions is true, then the CPU itself should have raised a GP
fault for the guest already (i.e. execution flow would never get
here).

Thanks, Jan