[MIPS] Linux sandbox: Allow __NR_send for mips32

This change will fix "Aw, Snap!" in Chromium for Linux on mips32,
which is caused by dissallowed __NR_send syscall:
sigsys_handlers.cc:**CRASHING**:seccomp-bpf failure in syscall 4000 + 0178

TEST=Running Chromium on MIPS CI20 board with 3.18 kernel
BUG=369594, 130022

Review URL: https://codereview.chromium.org/1666103002

Cr-Commit-Position: refs/heads/master@{#374357}

AUTHORS

@@ -408,6 +408,7 @@ Mihai Tica <mihai.o.tica@gmail.com>
 Mihai Tica <mitica@adobe.com>
 Mike Tilburg <mtilburg@adobe.com>
 Mikhail Pozdnyakov <mikhail.pozdnyakov@intel.com>
+Milko Leporis <milko.leporis@imgtec.com>
 Milton Chiang <milton.chiang@mediatek.com>
 Mingmin Xie <melvinxie@gmail.com>
 Minsoo Max Koo <msu.koo@samsung.com>

sandbox/linux/seccomp-bpf-helpers/syscall_sets.cc

@@ -550,7 +550,7 @@ bool SyscallSets::IsAllowedGeneralIo(int sysno) {
 #if defined(__i386__) || defined(__arm__) || defined(__mips__)
     case __NR__newselect:
 #endif
-#if defined(__arm__)
+#if defined(__arm__) || defined(__mips__)
     case __NR_send:
 #endif
 #if defined(__x86_64__) || defined(__arm__) || defined(__mips__) || \