ahci: EM message type auto detect

Detect enclosure management message type automatically at driver
initialization, instead of using module parameter "ahci_em_messages".

Signed-off-by: Harry Zhang <harry.zhang@amd.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

diff --cc drivers/ata/ahci.c
Simple merge

diff --cc drivers/ata/ahci.h
Simple merge

diff --cc drivers/ata/libahci.c
Simple merge