clk: at91: fix clk-generated parenting

[ Upstream commit 8e56133e5c7b7a7a97f6a92d92f664d5ecd30745 ]

clk_generated_startup is called after clk_hw_register. So the first call to
get_parent will not have the correct value (i.e. 0) and because this is
cached, it may never be updated.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Fixes: df70aeef ("clk: at91: add generated clock driver")
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>