drm/exynos: correct exynos_drm_fimd kerneldoc

Correct the kerneldoc of fimd_shadow_protect_win() to fix W=1 warnings:

  drivers/gpu/drm/exynos/exynos_drm_fimd.c:734: warning:
    expecting prototype for shadow_protect_win(). Prototype was for fimd_shadow_protect_win() instead
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_fimd.c

@@ -723,7 +723,7 @@ static void fimd_win_set_colkey(struct fimd_context *ctx, unsigned int win)
 }
 
 /**
- * shadow_protect_win() - disable updating values from shadow registers at vsync
+ * fimd_shadow_protect_win() - disable updating values from shadow registers at vsync
  *
  * @ctx: local driver data
  * @win: window to protect registers for