s390/dasd: Prepare for additional path event handling

s390/dasd: Prepare for additional path event handling

[ Upstream commit c94861e9dc73ca257a7e4e03b9f5600561888327 ]

As more path events need to be handled for ECKD the current path
verification infrastructure can be reused. Rename all path verifcation
code to fit the more broadly based task of path event handling and put
the path verification in a new separate function.

Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Stable-dep-of: 460e9bed82e4 ("s390/dasd: Fix potential memleak in dasd_eckd_init()")
Signed-off-by: Sasha Levin <sashal@kernel.org>