Fix two issues in lsusb-t.c

[naruto-abc]

One is a potential buffer overflow issue. Another one is to show that more speeds are supported in comments.

Both of two commits are quite easy and straightforward to understand.

[gregkh]

The "\n" is in the original file in sysfs, which is what this comment is saying. So changing this to only \0 is not correct :(

[gregkh]

This isn't an overflow as the kernel does not make the buffer bigger.

So this is an ok change, but perhaps clean up the changelog text?

Also, please properly wrap your changelog comments at 72 columns like your
editor asks you to :)