[ATA] Increase lba48 max-sectors from 200 to 256.

Also, moved ATA_MAX_SECTORS and ATA_MAX_SECTORS_LBA48 from
linux/libata.h to linux/ata.h, now that they truly reflect the standard
(well... mostly; note TODO comment).

This changes the performance profile (and potential bug profile)
for a bunch of drivers, so be wary.

include/linux/ata.h

@@ -40,6 +40,8 @@ enum {
 	ATA_MAX_DEVICES		= 2,	/* per bus/port */
 	ATA_MAX_PRD		= 256,	/* we could make these 256/256 */
 	ATA_SECT_SIZE		= 512,
+	ATA_MAX_SECTORS		= 256,
+	ATA_MAX_SECTORS_LBA48	= 65535,/* TODO: 65536? */
 
 	ATA_ID_WORDS		= 256,
 	ATA_ID_SERNO_OFS	= 10,