s390: chp: handle CRW_ERC_INIT for channel-path status change

When channel path is identified as the report source code (RSC)
of a CRW, and initialized (CRW_ERC_INIT) is recognized as the
error recovery code (ERC) by the channel subsystem, it indicates
a "path has come" event.

Let's handle this case in chp_process_crw().

Reviewed-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>