clk: meson: meson8b: fix the naming of the APB clocks

Fix a typo in the APB clock names by renaming them from "abp" to "apb".
No functional changes.

Fixes: a7d19b05 ("clk: meson: meson8b: add the CPU clock post divider clocks")
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Jerome Brunet <jbrunet@baylibre.com>
Link: https://lkml.kernel.org/r/20190210222603.6404-2-martin.blumenstingl@googlemail.com