net: tc35815: Explicitly check NET_IP_ALIGN is not zero in tc35815_rx

clang warns:

drivers/net/ethernet/toshiba/tc35815.c:1507:30: warning: use of logical
'&&' with constant operand [-Wconstant-logical-operand]
                        if (!HAVE_DMA_RXALIGN(lp) && NET_IP_ALIGN)
                                                  ^  ~~~~~~~~~~~~
drivers/net/ethernet/toshiba/tc35815.c:1507:30: note: use '&' for a
bitwise operation
                        if (!HAVE_DMA_RXALIGN(lp) && NET_IP_ALIGN)
                                                  ^~
                                                  &
drivers/net/ethernet/toshiba/tc35815.c:1507:30: note: remove constant to
silence this warning
                        if (!HAVE_DMA_RXALIGN(lp) && NET_IP_ALIGN)
                                                 ~^~~~~~~~~~~~~~~
1 warning generated.

Explicitly check that NET_IP_ALIGN is not zero, which matches how this
is checked in other parts of the tree. Because NET_IP_ALIGN is a build
time constant, this check will be constant folded away during
optimization.

Fixes: 82a9928d ("tc35815: Enable StripCRC feature")
Link: https://github.com/ClangBuiltLinux/linux/issues/608


Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>