Linux driver and CONFIG_KERNEL_DEBUG kernl build option

The Linux distribution that I’m using (it’s Slackware) recently switched from having CONFIG_KERNEL_DEBUG kernel build option set to “off” for the distribution provided kernel package, to having it set to “on”. However, recent releases of NVIDIA Linux drivers won’t build with this option set - following error is reported “GPL-incompatible module nvidia.ko uses GPL-only symbol ‘mutex_lock_nested’”. The solution is either to rebuild the kernel manually, with given option switched off, or eventually to fake that NVIDIA driver is GPL, by first unpacking the driver, and then changing strings MODULE_LICENCE(“NVIDIA”) to MODULE_LICENCE(“GPL”) throughout the driver source code. Obviously, neither is satisfactory, so I’m wondering would it be possible to make more appropriate change(s) in the driver source code, so that driver could be built with recent Linux kernel versions (it’s about 3.14.3 kernel in this particular case) even if kernel built with CONFIG_KERNEL_DEBUG option set to “on”?