ata: ahci: Drop pointless VPRINTK() calls and convert the remaining ones

Drop pointless VPRINTK() calls for entering and existing interrupt
routines and convert the remaining calls to dev_dbg().

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>