s390x: uv-host: Explain why we set up the home space and remove the

space change

UV home addresses don't require us to be in home space but we need to
have it set up so hw/fw can use the home asce to translate home
virtual addresses.

Hence we add a comment why we're setting up the home asce and remove
the address space since it's unneeded.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: Thomas Huth <thuth@redhat.com>