On userdebug & eng builds, change permission of SJTAG writable sysfs files that need to be written to 'system'. This became necessary after HSUM separated main user from the SYSTEM user
Bug: 367918586
Flag: EXEMPT bugfix
Test: Ensure that there is "Privileged Debugging" item in BetterBug settings.
Change-Id: Id433aea05d23841bb5b45b7b9464daa72602269b
Signed-off-by: Kostya Yarmash <kyarmash@google.com>