clk: uniphier: Fix fixed-rate initialization

Fixed-rate clocks in UniPhier don't have any parent clocks, however,
initial data "init.flags" isn't initialized, so it might be determined
that there is a parent clock for fixed-rate clock.

This sets init.flags to zero as initialization.

Cc: <stable@vger.kernel.org>
Fixes: 734d82f4a678 ("clk: uniphier: add core support code for UniPhier clock driver")
Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Link: https://lore.kernel.org/r/1646808918-30899-1-git-send-email-hayashi.kunihiko@socionext.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>