clk: imx7up: Rename the clks to hws

This is just to keep in line with the other i.MX clock drivers that are
clk_hw based. Plus, it makes more sense to be called hws since its type is
clk_hw not clk.

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>