accel/tcg: Assert that tlb fill gave us a valid TLB entry

accel/tcg: Assert that tlb fill gave us a valid TLB entry

In commit 4b1a3e1e34ad97 we added a check for whether the TLB entry
we had following a tlb_fill had the INVALID bit set.  This could
happen in some circumstances because a stale or wrong TLB entry was
pulled out of the victim cache.  However, after commit
68fea038553039e (which prevents stale entries being in the victim
cache) and the previous commit (which ensures we don't incorrectly
hit in the victim cache)) this should never be possible.

Drop the check on TLB_INVALID_MASK from the "is this a TLB_RECHECK?"
condition, and instead assert that the tlb fill procedure has given
us a valid TLB entry (or longjumped out with a guest exception).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20180713141636.18665-3-peter.maydell@linaro.org