linux-user: remove duplicate tswap32() from do_getsockopt()

linux-user: remove duplicate tswap32() from do_getsockopt()

This issue has been detected with tests/linux-tests.c:

linux-test.c:330: getsockopt

327     len = sizeof(val);
328     chk_error(getsockopt(server_fd, SOL_SOCKET, SO_TYPE, &val, &len));
329     if (val != SOCK_STREAM)
330         error("getsockopt");

In linux-user/syscall.c:do_getsockopt(), we have:
...
        val = tswap32(val);
...
            if (put_user_u32(val, optval_addr))
...

whereas "put_user_u32" calls in the end "__put_user" which uses "tswap32".

So the "val = tswap32(val);" is useless and wrong.

This patch removes it.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Riku Voipio <riku.voipio@iki.fi>