powerpc 8xx: defconfig: slice by 4 is more efficient than the default slice by 8 on Powerpc 8xx.

On PPC_8xx, CRC32_SLICEBY4 is more efficient (almost twice) than CRC32_SLICEBY8,
as shown below:

With CRC32_SLICEBY8:
[    1.109204] crc32: CRC_LE_BITS = 64, CRC_BE BITS = 64
[    1.114401] crc32: self tests passed, processed 225944 bytes in 15118910 nsec
[    1.130655] crc32c: CRC_LE_BITS = 64
[    1.134235] crc32c: self tests passed, processed 225944 bytes in 4479879 nsec

With CRC32_SLICEBY4:
[    1.097129] crc32: CRC_LE_BITS = 32, CRC_BE BITS = 32
[    1.101878] crc32: self tests passed, processed 225944 bytes in 8616242 nsec
[    1.116298] crc32c: CRC_LE_BITS = 32
[    1.119607] crc32c: self tests passed, processed 225944 bytes in 3289576 nsec
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Scott Wood <scottwood@freescale.com>

arch/powerpc/configs/adder875_defconfig

@@ -70,3 +70,4 @@ CONFIG_DEBUG_KERNEL=y
 CONFIG_DETECT_HUNG_TASK=y
 CONFIG_DEBUG_INFO=y
 # CONFIG_RCU_CPU_STALL_DETECTOR is not set
+CONFIG_CRC32_SLICEBY4=y

arch/powerpc/configs/ep88xc_defconfig

@@ -72,3 +72,4 @@ CONFIG_DEBUG_KERNEL=y
 CONFIG_DETECT_HUNG_TASK=y
 CONFIG_DEBUG_INFO=y
 # CONFIG_RCU_CPU_STALL_DETECTOR is not set
+CONFIG_CRC32_SLICEBY4=y

arch/powerpc/configs/mpc866_ads_defconfig

@@ -55,3 +55,4 @@ CONFIG_PARTITION_ADVANCED=y
 CONFIG_CRC_CCITT=y
 # CONFIG_RCU_CPU_STALL_DETECTOR is not set
 # CONFIG_CRYPTO_ANSI_CPRNG is not set
+CONFIG_CRC32_SLICEBY4=y

arch/powerpc/configs/mpc885_ads_defconfig

@@ -78,3 +78,4 @@ CONFIG_DEBUG_KERNEL=y
 CONFIG_DETECT_HUNG_TASK=y
 CONFIG_DEBUG_INFO=y
 # CONFIG_RCU_CPU_STALL_DETECTOR is not set
+CONFIG_CRC32_SLICEBY4=y

arch/powerpc/configs/tqm8xx_defconfig

@@ -84,3 +84,4 @@ CONFIG_DEBUG_KERNEL=y
 CONFIG_DETECT_HUNG_TASK=y
 CONFIG_DEBUG_INFO=y
 # CONFIG_RCU_CPU_STALL_DETECTOR is not set
+CONFIG_CRC32_SLICEBY4=y