scsi: core: fix scsi_host_queue_ready

32872863 ("scsi: avoid to hold host-wide counter of host_busy for
scsi_mq") adds one extra check on scsi_host_busy(shost) in
scsi_host_queue_ready(), which is wrong and not necessary, can causes
booting stall on LSI53c895A.

So remove the check.

Cc: Omar Sandoval <osandov@fb.com>,
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>,
Cc: James Bottomley <james.bottomley@hansenpartnership.com>,
Cc: Christoph Hellwig <hch@lst.de>,
Cc: Don Brace <don.brace@microsemi.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Laurence Oberman <loberman@redhat.com>
Cc: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Fixes: 32872863 ("scsi: avoid to hold host-wide counter of host_busy for scsi_mq")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>