clk: hisilicon: hi3519: add driver remove path and fix some issues

1. Add driver remove path.
2. Fix some issues.
   -Fix the ordering issue about clock provider being published.
   -Add error checking upon registering clocks.

Signed-off-by: Jiancheng Xue <xuejiancheng@hisilicon.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>