Update the comments for the ranges of cpu-used

Bug: aomedia:3223
Change-Id: I7c69be0cc2b7058cb50649d6bce0a37d8e0f4f33
(cherry picked from commit cc7d10c80fa9961f31434ace0d7ea8c4477afb93)

aom/aomcx.h

diff --git a/aom/aomcx.h b/aom/aomcx.h
index b8462e5..4a1c8bd 100644
--- a/aom/aomcx.h
+++ b/aom/aomcx.h
@@ -207,9 +207,13 @@
    * encoding process, values greater than 0 will increase encoder speed at
    * the expense of quality.
    *
-   * Valid range: 0..9. 0 runs the slowest, and 9 runs the fastest;
+   * Valid range: 0..10. 0 runs the slowest, and 10 runs the fastest;
    * quality improves as speed decreases (since more compression
    * possibilities are explored).
+   *
+   * NOTE: 10 is only allowed in AOM_USAGE_REALTIME. In AOM_USAGE_GOOD_QUALITY
+   * and AOM_USAGE_ALL_INTRA, 9 is the highest allowed value. However,
+   * AOM_USAGE_GOOD_QUALITY treats 7..9 the same as 6.
    */
   AOME_SET_CPUUSED = 13,
 

av1/arg_defs.c

diff --git a/av1/arg_defs.c b/av1/arg_defs.c
index 3b8c075..f62d060 100644
--- a/av1/arg_defs.c
+++ b/av1/arg_defs.c
@@ -289,9 +289,9 @@
   .max_intra_rate_pct =
       ARG_DEF(NULL, "max-intra-rate", 1, "Max I-frame bitrate (pct)"),
 #if CONFIG_AV1_ENCODER
-  .cpu_used_av1 =
-      ARG_DEF(NULL, "cpu-used", 1,
-              "Speed setting (0..6 in good mode, 6..9 in realtime mode)"),
+  .cpu_used_av1 = ARG_DEF(NULL, "cpu-used", 1,
+                          "Speed setting (0..6 in good mode, 6..10 in realtime "
+                          "mode, 0..9 in all intra mode)"),
   .rowmtarg =
       ARG_DEF(NULL, "row-mt", 1,
               "Enable row based multi-threading (0: off, 1: on (default))"),