hw/s390x: Fix bad mask in time2tod()

hw/s390x: Fix bad mask in time2tod()

Since "s390x/tcg: avoid overflows in time2tod/tod2time", the
time2tod() function tries to deal with the 9 uppermost bits in the
time value, but uses the wrong mask for this: 0xff80000000000000 should
be used instead of 0xff10000000000000 here.

Fixes: 14055ce53c2d901d826ffad7fb7d6bb8ab46bdfd
Cc: [email protected]
Signed-off-by: Thomas Huth <[email protected]>
Message-Id: <1544792887[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
[CH: tweaked commit message]
Signed-off-by: Cornelia Huck <[email protected]>