ARM: 8462/1: cache-uniphier: use common API to find the next level cache

The function uniphier_cache_get_next_level_node() does the same thing
as of_find_next_cache_node().  Drop the former and stick to the common
API.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>