IB/ipath: Avoid test_bit() on u64 SDMA status value

Gabriel C <nix.or.die@googlemail.com> pointed out that when the x86
bitops are updated to operate on unsigned long, the code in
sdma_abort_task() will produce warnings:

    drivers/infiniband/hw/ipath/ipath_sdma.c: In function 'sdma_abort_task':
    drivers/infiniband/hw/ipath/ipath_sdma.c:267: warning: passing argument 2 of 'constant_test_bit' from incompatible pointer type

and so on, because it uses test_bit() to operation on a u64 value
(returned by ipath_read_kref64() for a hardware register).

Fix up these warnings by converting the test_bit() operations to &ing
with appropriate symbolic defines of the bits within the hardware
register.  This has the benign side-effect of making the code more
self-documenting as well.

Signed-off-by: Roland Dreier <rolandd@cisco.com>