net/smc: fallback to TCP after connect problems

Correct the CLC decline reason codes for internal problems to not have
the sign bit set, negative reason codes are interpreted as not eligible
for TCP fallback.

Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>