libata: align ap->sector_buf

ap->sector_buf is used as DMA target and should at least be aligned on
cacheline.  This caused problems on some embedded machines.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

include/linux/libata.h

@@ -751,7 +751,8 @@ struct ata_port {
 	acpi_handle		acpi_handle;
 	struct ata_acpi_gtm	__acpi_init_gtm; /* use ata_acpi_init_gtm() */
 #endif
-	u8			sector_buf[ATA_SECT_SIZE]; /* owned by EH */
+	/* owned by EH */
+	u8			sector_buf[ATA_SECT_SIZE] ____cacheline_aligned;
 };
 
 /* The following initializer overrides a method to NULL whether one of