clk: imx8mm: add GPIO clocks to clock tree

clk: imx8mm: add GPIO clocks to clock tree

i.MX8MM has clock gate for each GPIO bank, add them
into clock tree for GPIO driver to manage.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>