mambo: Remove reliance on env(SIMHOST)
mambo: Remove reliance on env(SIMHOST)

The SIMHOST environment variable is not present in all version of
mambo.  This removes the reliance on it and instead uses the "display
default_configure" command to find the simulator type.

Signed-off-by: Michael Neuling <7b0ab45a730e48a69239010b5b8fe5fa4e8eaac6@neuling.org>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

mikey/skiboot,legoater/skiboot,legoater/skiboot,shenki/skiboot,shenki/skiboot,stewart-ibm/skiboot,stewart-ibm/skiboot,mikey/skiboot,mikey/skiboot,qemu/skiboot,open-power/skiboot,open-power/skiboot,shenki/skiboot,qemu/skiboot,open-power/skiboot,qemu/skiboot,open-power/skiboot,qemu/skiboot,legoater/skiboot,shenki/skiboot,legoater/skiboot,open-power/skiboot,qemu/skiboot,stewart-ibm/skiboot,shenki/skiboot,legoater/skiboot