clk: imx8mp: fix sai4 clock

clk: imx8mp: fix sai4 clock

The reference manual don't mention a SAI4 hardware block. This would be
clock slice 78 which is skipped (TRM, page 237). Remove any reference to
this clock to align the driver with the reality.

Fixes: 9c140d992676 ("clk: imx: Add support for i.MX8MP clock driver")
Acked-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Link: https://lore.kernel.org/r/20230731142150.3186650-1-m.felsch@pengutronix.de
Signed-off-by: Abel Vesa <abel.vesa@linaro.org>