Removal of checkboard from spl bootstrap build for SIMPC8313

This patch removes the checkboard function from the build of
the 4k bootstrap section for the SIMPC8313 as it is not needed
in the spl build.  This will allow > 100 bytes of extra room
for other uses.

Signed-off-by: Ron Madrid <ron_madrid@sbcglobal.net>
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>