shell: directory access to sysfs_net

This will allow bionic cts test to list network interfaces in
/sys/class/net.

Bug: 70537905
Test: adb shell /data/nativetest/bionic-unit-tests/bionic-unit-tests
--gtest_filter=ifaddrs.getifaddrs_interfaces
Change-Id: Ie07425fc54f9101e911962142824697e64d2bc45

public/shell.te

@@ -123,6 +123,9 @@ allow shell {
   proc_zoneinfo
 }:file r_file_perms;
 
+# allow listing network interfaces under /sys/class/net.
+allow shell sysfs_net:dir r_dir_perms;
+
 r_dir_file(shell, cgroup)
 allow shell domain:dir { search open read getattr };
 allow shell domain:{ file lnk_file } { open read getattr };