ART: unblock compiler tests on MIPS

The DCHECK() that's removed here causes most of compiler tests to
fail on MIPS. The issue is introduced with the recent changes in
the string dex cache.

Test: booted MIPS32 in QEMU
Test: test-art-target-run-test-optimizing on CI20

Change-Id: I7fd45fa0b6d64fbc553f6aeaa6dac7345c885fe4
1 file changed