spa: update blkptr diagram to include vdev padding on encrypted blocks

Probably just an oversight in 4d044c4c1d. SPA_VDEVBITS is always 24,
regardless of whether or not the bp is for an encrypted block, and it
wouldn't make sense for it to be different anyway.

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Alexander Motin <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Rob Norris <[email protected]>
Closes #17564

include/sys/spa.h

@@ -190,11 +190,11 @@ typedef struct zio_cksum_salt {
  *
  *	64	56	48	40	32	24	16	8	0
  *	+-------+-------+-------+-------+-------+-------+-------+-------+
- * 0	|		vdev1		| pad   |	  ASIZE		|
+ * 0	|  pad  |	  vdev1         | pad   |	  ASIZE		|
  *	+-------+-------+-------+-------+-------+-------+-------+-------+
  * 1	|G|			 offset1				|
  *	+-------+-------+-------+-------+-------+-------+-------+-------+
- * 2	|		vdev2		| pad   |	  ASIZE		|
+ * 2	|  pad  |	  vdev2         | pad   |	  ASIZE		|
  *	+-------+-------+-------+-------+-------+-------+-------+-------+
  * 3	|G|			 offset2				|
  *	+-------+-------+-------+-------+-------+-------+-------+-------+