wan: ds26522: select CONFIG_BITREVERSE

Without this, the driver runs into a link failure

arm-linux-gnueabi-ld: drivers/net/wan/slic_ds26522.o: in function `slic_ds26522_probe':
slic_ds26522.c:(.text+0x100c): undefined reference to `byte_rev_table'
arm-linux-gnueabi-ld: slic_ds26522.c:(.text+0x1cdc): undefined reference to `byte_rev_table'
arm-linux-gnueabi-ld: drivers/net/wan/slic_ds26522.o: in function `slic_write':
slic_ds26522.c:(.text+0x1e4c): undefined reference to `byte_rev_table'

Fixes: c37d4a00 ("Maxim/driver: Add driver for maxim ds26522")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>