clk: socfpga: use of_clk_add_hw_provider and improve error handling

clk: socfpga: use of_clk_add_hw_provider and improve error handling

The function of_clk_add_provider() has been deprecated, so use its
suggested replacement of_clk_add_hw_provider() instead.

Since of_clk_add_hw_provider() can fail, like of_clk_add_provider(),
check its return value and do the error handling.

The err variable unnecessarily duplicates the functionality of the
rc variable, so it has been removed.

Signed-off-by: Marco Pagani <marpagan@redhat.com>
Link: https://lore.kernel.org/r/20221209152913.1335068-4-marpagan@redhat.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>