[WireGuard] [PATCH] Add support for platforms which has no efficient unaligned memory access

[René van Dorst]

Here by my patch to support platforms which has no efficient unaligned  
memory access.

Without it, it caused 55.2% slowdown in throughput at TP-Link  
WR1043ND, MIPS32r2 at 400Mhz.

Benchmarks before:

root at lede:~# iperf3 -c 10.0.0.1 -i 10
[ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
[  4]   0.00-10.13  sec  28.8 MBytes  23.8 Mbits/sec    0    202 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.13  sec  28.8 MBytes  23.8 Mbits/sec    0             sender
[  4]   0.00-10.13  sec  28.8 MBytes  23.8 Mbits/sec                  receiver

root at lede:~# iperf3 -c 10.0.0.1 -i 10 -u -b 1G
[ ID] Interval           Transfer     Bandwidth       Total Datagrams
[  4]   0.00-10.00  sec  31.1 MBytes  26.1 Mbits/sec  3982
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Jitter     
Lost/Total Datagrams
[  4]   0.00-10.00  sec  31.1 MBytes  26.1 Mbits/sec  0.049 ms  0/3982 (0%)
[  4] Sent 3982 datagrams

Benchmarks with aligned memory fetching:

root at lede:~# iperf3 -c 10.0.0.1 -i 10
[ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
[  4]   0.00-10.22  sec  52.5 MBytes  43.1 Mbits/sec    0    145 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.22  sec  52.5 MBytes  43.1 Mbits/sec    0             sender
[  4]   0.00-10.22  sec  52.5 MBytes  43.1 Mbits/sec                  receiver

iperf Done.
root at lede:~# iperf3 -c 10.0.0.1 -i 10 -u -b 1G
[ ID] Interval           Transfer     Bandwidth       Total Datagrams
[  4]   0.00-10.00  sec  56.3 MBytes  47.2 Mbits/sec  7207
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Jitter     
Lost/Total Datagrams
[  4]   0.00-10.00  sec  56.3 MBytes  47.2 Mbits/sec  0.041 ms  0/7207 (0%)
[  4] Sent 7207 datagrams


Greats,

René van Dorst.