[CodeGenPrepare] Use APInt to check the value of the immediate in a and
while checking candidate for bit field extract.
Otherwise the value may not fit in uint64_t and this will trigger an
assertion.

This fixes PR19503.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206834 91177308-0d34-0410-b5e6-96231b3b80d8