MPILIB: Deobfuscate mpi_cmp

The condition preceding 'return 1;' makes my head hurt. At this point,
we know that u and v have the same sign; if they are negative, they
compare opposite to how their absolute values compare (which
mpihelp_cmp found for us), otherwise cmp itself is the
answer. Negating cmp is ok since mpihelp_cmp returns {-1,0,1};
-INT_MIN==INT_MIN won't bite us.

Signed-off-by: Rasmus Villemoes <[e-mail]>
Signed-off-by: David Howells <[e-mail]>
Acked-by: Dmitry Kasatkin <[e-mail]>

lib/mpi/mpi-cmp.c

···
 	if (!usize)
 		return 0;
 	cmp = mpihelp_cmp(u->d, v->d, usize);
-	if (!cmp)
-		return 0;
-	if ((cmp < 0 ? 1 : 0) == (u->sign ? 1 : 0))
-		return 1;
-	return -1;
+	if (u->sign)
+		return -cmp;
+	return cmp;
 }
 EXPORT_SYMBOL_GPL(mpi_cmp);