Fix incorrect LJ cut-off with GPU + PME tuning

Due to the mismatch of the macro used in generating and implementing the
twin cut-off CUDA kernels (used with PP-PME load balancing), the VdW
cut-off check was not generated and the (larger) electrostatics cut-off
was enforced instead, causing incorrect results with PME tuning.

Fixes #1603

Change-Id: I43ae19968b30843cfe407e927a5cf0bd35c62881