dell_s6000_s1220: add new line to end of i2ctools/series file

Commit a8408a4 introduced the use of cp-machine-patches to assemble
the patches for i2ctools.  cp-machine-patches has a problem if the
series files does not end with a newline.

This patch simply adds a new-line to the end of
machine/dell/dell_s6000_s1220/i2ctools/series.