IB/hns: Avoid compile test under non 64bit environments

The hns driver uses __raw_writeq which is only defined in 64BIT
environments. Trying to compile the driver in a 32BIT environment
results in errors. Only COMPILE_TEST when 64BIT is defined.

Fixes: 7d1b6a678e0b ("IB/hns: Support compile test for hns RoCE driver")
Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>