cmd_mem: cmp: unify size code paths

Not only does the source code get simpler, but it also shrinks the
compiled object code too.

While we're here, tweak the summary message to avoid the plural
issue.  It isn't that big of a deal, and it's currently wrong
anyways in the single (1 byte) case:
	Total of 1 byte were the same
Grammar wise, that should be "was" rather than "were".  The new
output people should be able to easily figure out:
	Total of 1 byte(s) were the same
	Total of 10 byte(s) were the same

Signed-off-by: Mike Frysinger <vapier@gentoo.org>