Mterp: Add missing shadow reg clear to op_long_to_double

Bug: 118647289
Test: ./art/test.py -b -r --target --32 --interpreter --gcstress -t 525
      with shadow_frame->CheckConsistentVRegs() added to MterpCheckBefore.
Change-Id: I49c12e9f5c8250b7172e0e8fae7c932b2eb10f69
1 file changed