drm/nouveau: fix u32 overflow in pushbuf reloc bounds check

In the Linux kernel, the following vulnerability has been resolved: drm/nouveau: fix u32 overflow in pushbuf reloc bounds check nouveau_gem_pushbuf_reloc_apply() validates each relocation with if (r->reloc_bo_offset + 4 > nvbo->bo.base.size) but reloc_bo_offset is __u32 (uapi/drm/nouveau_drm.h) and the integer literal 4 promotes to unsigned int, so the addition is performed in 32 bits and wraps before the comparison against the size_t bo size. Cast to u64 so the addition happens in 64-bit arithmetic. [ Add Fixes: tag. - Danilo ]