Fix SOCK_* flag definitions

MIPS and the rest of the world only disagree on the first two SOCK_*
constants, so restructure the #ifdef accordingly.

As a deliberate side effect, this fixes SOCK_DCCP being missing on
non-MIPS platforms.

Change-Id: I2267008f1121a7eebe1ed9097afab6e612bce7f0
Signed-off-by: Greg Hackmann <ghackmann@google.com>