soc: amlogic: meson-ee-pwrc: propagate errors from pm_genpd_init()

pm_genpd_init() can return an error. Propagate the error code to prevent
the driver from indicating that it successfully probed while there were
errors during pm_genpd_init().

Fixes: eef3c2ba

 ("soc: amlogic: Add support for Everything-Else power domains controller")
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>