Documentation/features: Update the ARCH_HAS_TICK_BROADCAST entry

Risc-V gained support recently.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/YN2nqOVHgGDt4Iid@gmail.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/features/time/arch-tick-broadcast/arch-support.txt

@@ -22,7 +22,7 @@
     |    openrisc: | TODO |
     |      parisc: | TODO |
     |     powerpc: |  ok  |
-    |       riscv: | TODO |
+    |       riscv: |  ok  |
     |        s390: | TODO |
     |          sh: |  ok  |
     |       sparc: | TODO |