drm/v3d: Remove unused function header

v3d_mmu_get_offset header was added but the function was never defined.
Just remove it.
Signed-off-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231130164420.932823-3-mcanal@igalia.com

drivers/gpu/drm/v3d/v3d_drv.h

@@ -420,8 +420,6 @@ void v3d_irq_disable(struct v3d_dev *v3d);
 void v3d_irq_reset(struct v3d_dev *v3d);
 
 /* v3d_mmu.c */
-int v3d_mmu_get_offset(struct drm_file *file_priv, struct v3d_bo *bo,
-		       u32 *offset);
 int v3d_mmu_set_page_table(struct v3d_dev *v3d);
 void v3d_mmu_insert_ptes(struct v3d_bo *bo);
 void v3d_mmu_remove_ptes(struct v3d_bo *bo);