x86: Move invalidateTLBEntry in unmapPage
x86: Move invalidateTLBEntry in unmapPage

invalidateTLBEntry is currently called twice in unmapPage
Once behind a guard that only performs the invalidate if
the active vspace is the same as the one that contains the
mapping, and then a second time at the end of unmapPage
without any guard at all.

This commit removes the unguarded version and replaces it
with the guarded one from earlier in the function.

zhicheng/seL4,cmr/seL4,zhicheng/seL4,zhicheng/seL4,cmr/seL4,cmr/seL4