Common i/o layer changes:
 - Fix error handling in io_subchannel_register.
 - Fix __MAX_SUBCHANNELS limit checking.
 - Clear slow_subchannel structure after kmalloc.
 - Update ssd_info if a different device appears at an already known
   subchannel to get the correct set of chpids.
 - Avoid struct initializers to reduce stack usage of ccwgroup_create,
   readall_cmb and io_subchannel_recog,
 - Setup fields in pmcw in each retry because msch might fail and a stsch
   overwrites them.
 - Prevent irq_exit() in cio_tpi from calling do_softirq by adding a
   local_bh_disable/__local_bh_enable pair.
 - Retry sense id after receiving an unsolicited interrupt.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>