Now that we have a bootm command which boots everything we can
simplify the defaultenvironment. We can call bootm on every
image type and can remove the kernelimage_type variables.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Patrice Vilchez <patrice.vilchez@atmel.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>