m68k: fix some comment spelling errors

m68k: fix some comment spelling errors

I found that there are many spelling errors in the comments of qemu/target/m68k.
I used spellcheck to check the spelling errors and found some errors in the folder.

Signed-off-by: zhaolichang <zhaolichang@huawei.com>
Reviewed-by: David Edmondson <david.edmondson@oracle.com>
Reviewed-by: Philippe Mathieu-Daude<f4bug@amsat.org>
Reviewed-by: Laurent Vivier<laurent@vivier.eu>
Message-Id: <20201009064449.2336-9-zhaolichang@huawei.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>