IPoIB: Always build debugging code unless CONFIG_EMBEDDED=y

Don't allow CONFIG_INFINIBAND_IPOIB_DEBUG to be disabled unless
CONFIG_EMBEDDED is selected.  We want users (and especially distros)
to have this turned on unless they really need to save space, because
by the time we want debugging output, it's usually too late to rebuild
a kernel.  The debugging output can be controlled at runtime via the
debug_level module parameter in sysfs.

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