clk: imx: imx6ul: Move csi_sel mux to correct base register

The csi_sel mux register is located in the CCM register base and not the
CCM_ANALOG register base. So move it to the correct position in code.

Otherwise changing the parent of the csi clock can lead to a complete
system failure due to the CCM_ANALOG_PLL_SYS_TOG register being falsely
modified.

Also remove the SET_RATE_PARENT flag since one possible supply for the
csi_sel mux is the system PLL which we don't want to modify.

Signed-off-by: Stefan Riedmueller <s.riedmueller@phytec.de>
Reviewed-by: Abel Vesa <abel.vesa@nxp.com>
Link: https://lore.kernel.org/r/20210927072857.3940880-1-s.riedmueller@phytec.de
Signed-off-by: Abel Vesa <abel.vesa@nxp.com>