clk: meson: meson8b: fix meson8b_cpu_clk parent clock name

meson8b_cpu_clk has two parent clocks:
- meson8b_xtal
- meson8b_cpu_scale_out_sel

The name of the "xtal" clock parent is specified correctly. However,
there is a typo in the name of the second parent clock. The
meson8b_cpu_scale_out_sel definition uses the name "cpu_scale_out_sel"
(which matches the name from the datasheet). However, the mux parent
definition uses the name "cpu_out_sel" which does not match any existing
clock.

Fixes: 251b6fd3 ("clk: meson: rework meson8b cpu clock")
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>