fbdev/simplefb: Suppress error on missing power domains

When the power domains are missing, the call to of_count_phandle_with_args
fails with -ENOENT. The power domains are not required and there are
some device trees that do not specify them. Suppress this error to fix
devices without power domains attached to simplefb.

Fixes: 92a511a5 ("fbdev/simplefb: Add support for generic power-domains")
Closes: https://lore.kernel.org/linux-fbdev/ZVwFNfkqjrvhFHM0@radian


Signed-off-by: Richard Acayan <mailingradian@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231122005457.330066-3-mailingradian@gmail.com