ide: decrease size of ->pc_buf field in struct ide_atapi_pc

struct ide_atapi_pc is often allocated on the stack and size of ->pc_buf
size is 256 bytes. However since only ide_floppy_create_read_capacity_cmd()
and idetape_create_inquiry_cmd() require such size allocate buffers for
these pc-s explicitely and decrease ->pc_buf size to 64 bytes.

Cc: Borislav Petkov <[e-mail]>
Signed-off-by: Bartlomiej Zolnierkiewicz <[e-mail]>

drivers/ide/ide-floppy.c

···
 	struct gendisk *disk = floppy->disk;
 	struct ide_atapi_pc pc;
 	u8 *cap_desc;
-	u8 header_len, desc_cnt;
+	u8 pc_buf[256], header_len, desc_cnt;
 	int i, rc = 1, blocks, length;
 
 	drive->bios_cyl = 0;
···
 	drive->capacity64 = 0;
 
 	ide_floppy_create_read_capacity_cmd(&pc);
+	pc.buf = &pc_buf[0];
+	pc.buf_size = sizeof(pc_buf);
+
 	if (ide_queue_pc_tail(drive, disk, &pc)) {
 		printk(KERN_ERR PFX "Can't get floppy parameters\n");
 		return 1;

drivers/ide/ide-floppy_ioctl.c

···
 					    int __user *arg)
 {
 	struct ide_disk_obj *floppy = drive->driver_data;
-	u8 header_len, desc_cnt;
 	int i, blocks, length, u_array_size, u_index;
 	int __user *argp;
+	u8 pc_buf[256], header_len, desc_cnt;
 
 	if (get_user(u_array_size, arg))
 		return -EFAULT;
···
 		return -EINVAL;
 
 	ide_floppy_create_read_capacity_cmd(pc);
+	pc->buf = &pc_buf[0];
+	pc->buf_size = sizeof(pc_buf);
+
 	if (ide_queue_pc_tail(drive, floppy->disk, pc)) {
 		printk(KERN_ERR "ide-floppy: Can't get floppy parameters\n");
 		return -EIO;

drivers/ide/ide-tape.c

···
 {
 	idetape_tape_t *tape = drive->driver_data;
 	struct ide_atapi_pc pc;
+	u8 pc_buf[256];
 	char fw_rev[4], vendor_id[8], product_id[16];
 
 	idetape_create_inquiry_cmd(&pc);
+	pc.buf = &pc_buf[0];
+	pc.buf_size = sizeof(pc_buf);
+
 	if (ide_queue_pc_tail(drive, tape->disk, &pc)) {
 		printk(KERN_ERR "ide-tape: %s: can't get INQUIRY results\n",
 				tape->name);

include/linux/ide.h

···
  * With each packet command, we allocate a buffer of IDE_PC_BUFFER_SIZE bytes.
  * This is used for several packet commands (not for READ/WRITE commands).
  */
-#define IDE_PC_BUFFER_SIZE	256
+#define IDE_PC_BUFFER_SIZE	64
 #define ATAPI_WAIT_PC		(60 * HZ)
 
 struct ide_atapi_pc {