Documentation/features: Add kcov

Add an arch support status file for kcov (ARCH_HAS_KCOV).
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Link: https://lore.kernel.org/r/20200627092300.29438-1-tklauser@distanz.chSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/features/debug/kcov/arch-support.txt

+#
+# Feature name:          kcov
+#         Kconfig:       ARCH_HAS_KCOV
+#         description:   arch supports kcov for coverage-guided fuzzing
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: | TODO |
+    |         arm: |  ok  |
+    |       arm64: |  ok  |
+    |         c6x: | TODO |
+    |        csky: | TODO |
+    |       h8300: | TODO |
+    |     hexagon: | TODO |
+    |        ia64: | TODO |
+    |        m68k: | TODO |
+    |  microblaze: | TODO |
+    |        mips: |  ok  |
+    |       nds32: | TODO |
+    |       nios2: | TODO |
+    |    openrisc: | TODO |
+    |      parisc: | TODO |
+    |     powerpc: |  ok  |
+    |       riscv: |  ok  |
+    |        s390: |  ok  |
+    |          sh: | TODO |
+    |       sparc: | TODO |
+    |          um: |  ok  |
+    |   unicore32: | TODO |
+    |         x86: |  ok  |
+    |      xtensa: | TODO |
+    -----------------------