s390/pai: Calculate size of reserved PAI extension control block area

The PAI extension 1 control block area is 512 bytes in total.
It currently contains three address pointer which refer to counter
memory blocks followed by a reserved area.
Calculate the reserved area instead of hardcoding its size. This
makes the code more readable and maintainable.
No functional chance.

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Suggested-by: Jan Polensky <japo@linux.ibm.com>
Reviewed-by: Jan Polensky <japo@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Author: Thomas Richter

arch/s390/kernel/perf_pai.c

@@ -48,7 +48,7 @@ struct paiext_cb {		/* PAI extension 1 control block */
 	u64 header;		/* Not used */
 	u64 reserved1;
 	u64 acc;		/* Addr to analytics counter control block */
-	u8 reserved2[488];
+	u8 reserved2[PAIE1_CTRBLOCK_SZ - 3 * sizeof(u64)];
 } __packed;
 
 struct pai_map {