Use ro.logd.kernel for kernel logcat

Prevent a possible DOS of the kernel logs because the runtime result
could differ from the boottime result.

Test: adb bugreport, then examine kernel log
Change-Id: I140fd465f2e691c751d92af50dbdf95e23c121d8
diff --git a/logd/README.property b/logd/README.property
index de6767a..da5f96f 100644
--- a/logd/README.property
+++ b/logd/README.property
@@ -31,9 +31,9 @@
                                          resist increasing the log buffer.
 persist.logd.size.<buffer> number  ro    Size of the buffer for <buffer> log
 ro.logd.size.<buffer>      number svelte default for persist.logd.size.<buffer>
-ro.config.low_ram          bool   false  if true, logd.statistics, logd.kernel
-                                         default false, logd.size 64K instead
-                                         of 256K.
+ro.config.low_ram          bool   false  if true, logd.statistics,
+                                         ro.logd.kernel default false,
+                                         logd.size 64K instead of 256K.
 persist.logd.filter        string        Pruning filter to optimize content.
                                          At runtime use: logcat -P "<string>"
 ro.logd.filter       string "~! ~1000/!" default for persist.logd.filter.