netdev-linux: Fix unaligned access to rpl_rtnl_link_stats64. #3048

Job	Run time
dpdk gcc	4s
osx clang --disable-ssl	1m 31s
linux rpm fedora	4m 14s
linux deb no dpdk	4m 36s
clang-analyze	18m 49s
linux gcc --disable-ssl	2m 39s
linux clang --disable-ssl	2m 34s
linux gcc c99	2m 28s
linux clang c99	2m 37s
linux gcc test	8m 13s
linux clang address,undefined test	16m 23s
linux gcc test --enable-shared	11m 19s
linux clang test --enable-shared	11m 40s
linux gcc check check-dpdk dpdk	18m 43s
linux clang check check-dpdk dpdk	18m 20s
linux gcc test -ljemalloc	8m 39s
linux clang test -ljemalloc	8m 54s
linux gcc --enable-afxdp	2m 25s
linux clang --enable-afxdp	2m 37s
linux gcc dpdk --enable-shared	3m 24s
linux clang dpdk --enable-shared	3m 31s
linux gcc dpdk-shared	2m 37s
linux clang dpdk-shared	2m 47s
linux gcc dpdk-shared --enable-shared	3m 17s
linux clang dpdk-shared --enable-shared	3m 43s
linux gcc m32 --disable-ssl	2m 41s
linux gcc check-ovsdb-cluster	6m 46s
linux gcc check-kernel -100	9m 14s
linux gcc check-kernel 100-	9m 27s
linux clang address,undefined check-kernel -100	11m 36s
linux clang address,undefined check-kernel 100-	11m 56s
linux gcc check-offloads -100	9m 6s
linux gcc check-offloads 100-	7m 46s
linux gcc dpdk check-system-userspace	10m 44s
linux clang address,undefined dpdk check-system-userspace	15m 7s
linux gcc dpdk check-system-tso	10m 51s
linux gcc dpdk check-afxdp	12m 11s
	4h 43m 29s

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