libsel4utils vspace assumes it is managing sel4 userspace but is also used for vm guests

[kent-mcleod]

(Imported from https://sel4.atlassian.net/browse/SELFOUR-2440)
It directly assumes it is managing a sel4 userlevel virtual address space with a kernel window at the top and rejects any mappings that would normally fall into the kernel window, but isn't a valid constraint for guests. So on ia32 trying to create devices above 0xe0000000 in the guest fails.