clk: imx: gate3: Switch to clk_hw based API

Switch the imx_clk_hw_gate3_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>