clk: imx8mp: fix usb_root_clk parent

According to reference mannual CCGR77(usb) sources from hsio_axi, fix
it.

Fixes: 9c140d99

 ("clk: imx: Add support for i.MX8MP clock driver")
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Abel Vesa <abel.vesa@nxp.com>
Link: https://lore.kernel.org/r/20220507125430.793287-1-peng.fan@oss.nxp.com


Signed-off-by: Abel Vesa <abel.vesa@nxp.com>