Temporarily allow non ro. props to be Readonly

Some properties don't have prefix "ro." but not written in any Java or
C++ codes. They might be misnamed and should be readonly. This commit
temporarily allows such properties to be Readonly, in order to migrate
them fast.

Bug: 117924132
Test: mma -j && sysprop_test
Change-Id: Ibcda0cbc0f4d4dc6e4781947264ce20d169115ba