[SCSI] megaraid_sas: Move poll_aen_lock initializer

The following patch moves the poll_aen_lock initializer from
megasas_probe_one() to megasas_init().  This prevents a crash when a user
loads the driver and tries to issue a poll() system call on the ioctl
interface with no adapters present.

Signed-off-by: Kashyap Desai <Kashyap.Desai@lsi.com>
Signed-off-by: Adam Radford <aradford@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>