of: dynamic: Fix of_reconfig_get_state_change() return value documentation

of: dynamic: Fix of_reconfig_get_state_change() return value documentation

The documented numeric return values do not match the actual returned
values. Fix them by using the enum names instead of raw numbers.

Fixes: b53a2340d0d3 ("of/reconfig: Add of_reconfig_get_state_change() of notifier helper.")
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Link: https://lore.kernel.org/r/20231123-fix-of_reconfig_get_state_change-docs-v1-1-f51892050ff9@bootlin.com
Signed-off-by: Rob Herring <robh@kernel.org>