riscv64: increase ASLR randomness for Sv48/57

Linux 6.9+ supports 33 bits with Sv48 and Sv57. Increase the
maximum and update the comment.

Bug: https://github.com/google/android-riscv64/issues/1
Test: Treehugger
Change-Id: Ia2731143ad30c5febe2058d35a381c01b14d8c3c
1 file changed