[X86] Avoid miscompile in combineOr (X86ISelLowering.cpp)

In combineOr (X86ISelLowering.cpp) there is a DAG combine that rewrite
a "(0 - SetCC) | C" pattern into something simpler given that a LEA
can be used. Another requirement is that C has some specific value,
for example 1 or 7. When checking those requirements the code used a
32-bit unsigned variable to store the value of C. So for a 64-bit OR
this could miscompile in case any of the 32 most significant bits in
C were non zero.

This patch adds fixes the bug by using a large enough type for the
C value.

The faulty code seem to have been introduced by commit 9bceb898
(D131358).

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D134892