scsi: ipr: Add asynchronous error notification

This patch implements functions for pushing HCAM (host controlled
asynchronous messages) error buffers to userspace through sysfs
attributes.  Reads to the "async_err_log" attribute will result in a
single HCAM buffer being copied to userspace; one can process the next
HCAM buffer by writing any string to the same attribute.

A new list was added to the ioa_cfg structure to store the HCAM buffers
for later reporting. We also send a KOBJ_CHANGE event whenever a new
HCAM buffer is made available to userspace.

Signed-off-by: Heitor Ricardo Alves de Siqueira <halves@linux.vnet.ibm.com>
Signed-off-by: Gabriel Krisman Bertazi <krisman@linux.vnet.ibm.com>
Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>