clk: imx: Rename the imx_clk_pfdv2 to imply it's clk_hw based

Renaming the imx_clk_pfdv2 register function to imx_clk_hw_pfdv2 to be
more obvious it is clk_hw based.

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