Remove unnecessary HCTR2 macro in libfscrypt

The HCTR2 definition is no longer needed since the 6.0 kernel headers
were pulled into Android in change
I282de83f23b432bef58214108a93700bdadddf0f

Bug: 233652475
Test: Ensured that code still compiles and CTS test still passes
Change-Id: I331128a2f8f20a39d41a984902732d19511b8d1e
1 file changed