[S390] Hypervisor filesystem (s390_hypfs) for z/VM

This is an extension of the already existing hypfs for LPAR (DIAG 204).
Data returned by DIAG 2fc is exported using the s390_hypfs when Linux
is running under z/VM. Information about cpus and memory is provided.
Data is put into different virtual files which can be accessed from user
space. All values are represented as ASCII strings

Signed-off-by: Michael Holzheu <holzheu@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>