powerpc/code-patching: Fix patch_branch() return on out-of-range failure

Do not silentely ignore a failure of create_branch() in
patch_branch(). Return -ERANGE.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/8540cb64b1f06710eaf41e3835c7ba3e21fa2b05.1638446239.git.christophe.leroy@csgroup.eu