allow shell dmesg

Allow the shell user to see the dmesg output. This data is already
available via "adb bugreport", but isn't easy to access.

Bug: 10020939
Change-Id: I9d4bbbd41cb02b707cdfee79f826a39c1ec2f177
diff --git a/shelldomain.te b/shelldomain.te
index 0a86426..3dd0941 100644
--- a/shelldomain.te
+++ b/shelldomain.te
@@ -32,3 +32,6 @@
 # Directory read access and file write access is already granted
 # in domain.te.
 allow shelldomain debugfs:file r_file_perms;
+
+# allow shell to run dmesg
+allow shelldomain kernel:system syslog_read;