clk: Add kerneldoc to managed of-provider interfaces

Document the devm_of_clk_del_provider and the
devm_of_clk_add_hw_provider functions.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
[sboyd@kernel.org: Comply with kernel-doc formatting]
Signed-off-by: Stephen Boyd <sboyd@kernel.org>