clk: imx: clk-composite-8m: Switch to clk_hw based API

Switch the imx8m_clk_hw_composite_flags function to clk_hw based API,
rename accordingly and add a macro for clk based legacy. This allows
us to move closer to a clear split between consumer and provider clk
APIs.

Reviewed-by: Abel Vesa <abel.vesa@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>