ia64: boolean __test_and_clear_bit

__test_and_clear_bit() returns a bitfield with the tested-for bit set.
Make it consistent with the other bitops - of ia64 but also every
other architecture - and return a boolean value.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Fenghua Yu <fenghua.yu@intel.com>