ART: ARM64: Pass ISA features to VIXL macroassembler.

VIXL macroassembler should be initialized properly
to support Armv8.X features in order to emit corresponding
instructions.

Test: codegen_test.cc, relative_patcher_arm64_test.
Test: test-art-host, test-art-target.
Change-Id: I2f9e155c28b4d2252a3cfb19717f5d25824d5e11