crypto: crypto4xx - increase context and scatter ring buffer elements

If crypto4xx is used in conjunction with dm-crypt, the available
ring buffer elements are not enough to handle the load properly.

On an aes-cbc-essiv:sha256 encrypted swap partition the read
performance is abyssal: (tested with hdparm -t)

/dev/mapper/swap_crypt:
 Timing buffered disk reads:  14 MB in  3.68 seconds =   3.81 MB/sec

The patch increases both PPC4XX_NUM_SD and PPC4XX_NUM_PD to 256.
This improves the performance considerably:

/dev/mapper/swap_crypt:
 Timing buffered disk reads: 104 MB in  3.03 seconds =  34.31 MB/sec

Furthermore, PPC4XX_LAST_SD, PPC4XX_LAST_GD and PPC4XX_LAST_PD
can be easily calculated from their respective PPC4XX_NUM_*
constant.

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/amcc/crypto4xx_core.h

@@ -36,12 +36,12 @@
 #define PPC405EX_CE_RESET                       0x00000008
 
 #define CRYPTO4XX_CRYPTO_PRIORITY		300
-#define PPC4XX_LAST_PD				63
-#define PPC4XX_NUM_PD				64
-#define PPC4XX_LAST_GD				1023
+#define PPC4XX_NUM_PD				256
+#define PPC4XX_LAST_PD				(PPC4XX_NUM_PD - 1)
 #define PPC4XX_NUM_GD				1024
-#define PPC4XX_LAST_SD				63
-#define PPC4XX_NUM_SD				64
+#define PPC4XX_LAST_GD				(PPC4XX_NUM_GD - 1)
+#define PPC4XX_NUM_SD				256
+#define PPC4XX_LAST_SD				(PPC4XX_NUM_SD - 1)
 #define PPC4XX_SD_BUFFER_SIZE			2048
 
 #define PD_ENTRY_INUSE				1