Smatch complains that the error path where "action" is invalid leaks
the "ce" allocation:
    drivers/of/dynamic.c:935 of_changeset_action()
    warn: possible memory leak of 'ce'

Fix this by doing the validation before the allocation.

Note that there is not any actual problem with upstream kernels. All
callers of of_changeset_action() are static inlines with fixed action
values.

Fixes: 914d9d83 ("of: dynamic: Refactor action prints to not use "%pOF" inside devtree_lock")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/r/202309011059.EOdr4im9-lkp@intel.com/Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/7dfaf999-30ad-491c-9615-fb1138db121c@moroto.mountainSigned-off-by: Rob Herring <robh@kernel.org>