powerpc/module: Fix stubs for BE

A simple patch which was supposed to swap r12 and r11 also
inexplicably changed the offset by two bytes.  This instruction
(to load r2) isn't used in LE, so it wasn't noticed.

Fixes: b1ce369e ("powerpc: modules: use r12 for stub jump address.)
Reported-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Tested-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>