kernel: fix crashes on MIPS when loading kernel modules under memory pressure

When memory is tight, modules may need to be loaded into vmalloc()
space. The code then has to generate jump trampolines which enable
relocations between vmalloc space and physical address space.

The code had a bug that was freeing these trampolines even when the
module was successfully loaded.

Signed-off-by: Felix Fietkau <nbd@nbd.name>