clk: add api to get clk consumer from clk_hw

clk: add api to get clk consumer from clk_hw

clk_register() is deprecated. Using 'clk' member of struct clk_hw is
discouraged. With this constraint, it is difficult for driver to
register clocks using the clk_hw API and then use the clock with
the consumer API

This adds a simple helper, clk_hw_get_clk(), to get a struct clk from
a struct clk_hw. Like other clk_get() variant, each call to this helper
must be balanced with a call to clk_put(). To make life easier on the
consumers, a memory managed version is provided as well.

Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Link: https://lore.kernel.org/r/20201021162147.563655-3-jbrunet@baylibre.com
Tested-by: Kevin Hilman <khilman@baylibre.com>
[sboyd@kernel.org: Fix kernel-doc]
Signed-off-by: Stephen Boyd <sboyd@kernel.org>