core/test: Use skiboot's own malloc for mem_region tests
core/test: Use skiboot's own malloc for mem_region tests

Comments in the run-mem_region test imply that it uses skiboot's own
malloc for the malloc implementation, but this isn't true; a malloc
inside the mem_region code itself will use the glibc malloc.

This change implements the intention of the test, and uses skiboot
malloc for the file-under-test. real_malloc() is available for actual
glibc mallocs.

Signed-off-by: Jeremy Kerr <68a658b44bbaefab3ef5cd231967195fc0ff9d69@ozlabs.org>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

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