mambo: print useful error when mysim mmap fails
mambo: print useful error when mysim mmap fails

My user id didn't have access to disk.img and the code printed
the error message:

ERROR: pmem: 'mysim mmap' command needs newer mambo

mysim mmap has been in Mambo for a while so this patch prints out the
error message from catch.  Now we get the useful:

ERROR: pmem: 'mysim mmap' Error opening file disk.img for mapping

Signed-off-by: Ryan Grimm <b82eecdfce19ef6c0125840b498d3afc6226dd31@linux.ibm.com>
Reviewed-by: Dan Horák <2591e5f46f28d303f9dc027d475a5c60d8dea17a@danny.cz>
Signed-off-by: Reza Arbab <4c896a97e6b998365c2d50a267b0f1ca5f7995de@linux.ibm.com>

qemu/skiboot,open-power/skiboot,open-power/skiboot,open-power/skiboot,qemu/skiboot,open-power/skiboot,qemu/skiboot,open-power/skiboot,qemu/skiboot,qemu/skiboot