[PATCH] libata: remove unused HSM_ST_UNKNOWN

HSM_ST_UNKNOWN is not used anywhere.  Its value is zero and supposed
to serve sanity check purpose but HSM_ST_IDLE is used for that
purpose.  This unused state causes confusion.  After a port is
initialized but before the first command is executed, the idle hsm
state is UNKNOWN.  However, once a command has completed, the idle hsm
state is IDLE.  This defeats sanity check in ata_pio_task() for the
first command.

This patch removes HSM_ST_UNKNOWN and consequently make HSM_ST_IDLE
the default state.

Signed-off-by: Tejun Heo <htejun@gmail.com>

include/linux/libata.h

@@ -318,7 +318,6 @@ enum {
 };
 
 enum hsm_task_states {
-	HSM_ST_UNKNOWN,		/* state unknown */
 	HSM_ST_IDLE,		/* no command on going */
 	HSM_ST,			/* (waiting the device to) transfer data */
 	HSM_ST_LAST,		/* (waiting the device to) complete command */