Documentation/features/time: Mark m68k having modern-timekeeping

M68k no longer uses arch_gettimeoffset.
Signed-off-by: NGeert Uytterhoeven <geert@linux-m68k.org>

Documentation/features/time/modern-timekeeping/arch-support.txt

@@ -15,7 +15,7 @@
     |       h8300: |  ok  |
     |     hexagon: |  ok  |
     |        ia64: |  ok  |
-    |        m68k: | TODO |
+    |        m68k: |  ok  |
     |  microblaze: |  ok  |
     |        mips: |  ok  |
     |       nds32: |  ok  |