Add a new Coccinelle script which replaces uses of the inplace
byteswapping functions *_to_cpus() and cpu_to_*s() with their
not-in-place equivalents. This is useful for where the swapping
is done on members of a packed struct -- taking the address
of the member to pass it to an inplace function is undefined
behaviour in C.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20181009181612.10633-1-peter.maydell@linaro.org