powerpc/configs: Drop no longer needed CONFIG_IPV6

Since commit de551f2e ("net: Build IPv6 into kernel by default")
we no longer need to set CONFIG_IPV6 in our defconfigs.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/configs/85xx/xes_mpc85xx_defconfig

@@ -54,7 +54,6 @@ CONFIG_IP_PIMSM_V2=y
 # CONFIG_INET_XFRM_MODE_TRANSPORT is not set
 # CONFIG_INET_XFRM_MODE_TUNNEL is not set
 # CONFIG_INET_XFRM_MODE_BEET is not set
-CONFIG_IPV6=y
 CONFIG_UEVENT_HELPER_PATH="/sbin/hotplug"
 CONFIG_MTD=y
 CONFIG_MTD_REDBOOT_PARTS=y

arch/powerpc/configs/cell_defconfig

@@ -52,7 +52,6 @@ CONFIG_IP_PNP_RARP=y
 CONFIG_NET_IPIP=y
 CONFIG_SYN_COOKIES=y
 # CONFIG_INET_XFRM_MODE_BEET is not set
-CONFIG_IPV6=y
 CONFIG_INET6_AH=m
 CONFIG_INET6_ESP=m
 CONFIG_INET6_IPCOMP=m