s390/ap: implement SE AP bind, unbind and associate

Implementation of the new functions for SE AP support:
bind, unbind and associate. There are two new sysfs
attributes for this:

/sys/devices/ap/cardxx/xx.yyyy/se_bind
/sys/devices/ap/cardxx/xx.yyyy/se_associate

Writing a 1 into the se_bind attribute triggers the
SE AP bind for this AP queue, writing a 0 into does
an unbind - that's a reset (RAPQ) with the F bit enabled.

The se_associate attribute needs an integer value in
range 0...2^16-1 written in. This is the index into a
secrets table feed into the ultravisor. For more details
please see the Architecture documents.

These both new ap queue attributes are only visible
inside a SE guest with SB (Secure Binding) available.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Holger Dengler <dengler@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>