Fixed access to freed memory in ShiftShiftShift2ShiftShift 1a on ARM

ShiftShiftShift2ShiftShift tried to access a wrong and already freed
instruction the find out whatever a shift will result in a 0 result.

For some reason this only resulted in a bug on x86_64 linux host
crosscompiler builds.

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@23624 3ad0048d-3df7-0310-abae-a5850022a9f2