of: overlay: Remove else after goto

If an "if" branch is terminated by a "goto", there's no need to have an
"else" statement and an indented block of code.

Remove the "else" statement to simplify the code flow for the casual
reviewer.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rob Herring <robh@kernel.org>