sunxi: Use kernel specific sub target configuration

To make it easier to support multiple kernel versions in parallel also
copy the sub target specific kernel configurations into kernel specific
files.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

diff --git a/target/linux/sunxi/cortexa53/config-default b/target/linux/sunxi/cortexa53/config-4.14
similarity index 100%
rename from target/linux/sunxi/cortexa53/config-default
rename to target/linux/sunxi/cortexa53/config-4.14

diff --git a/target/linux/sunxi/cortexa7/config-default b/target/linux/sunxi/cortexa7/config-4.14
similarity index 100%
rename from target/linux/sunxi/cortexa7/config-default
rename to target/linux/sunxi/cortexa7/config-4.14

diff --git a/target/linux/sunxi/cortexa8/config-default b/target/linux/sunxi/cortexa8/config-4.14
similarity index 100%
rename from target/linux/sunxi/cortexa8/config-default
rename to target/linux/sunxi/cortexa8/config-4.14