clk: Add devm_clk_get()

Add a resource managed clk_get() to simplify clock usage in
drivers. This allows driver authors to "get and forget" about
their clocks by automatically calling clk_put() when the driver
is detached. This also encourages clock consumers to use the
clk_get() API correctly by passing in a struct device as an
argument.

Change-Id: I1ed53cd3c26c0390fa30cd3c3dca14bcdd59939f
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>