[InstComobineCalls] Fix buildbot failures after r294453.

Some targets don't support uint64_t options. Change type to unsigned.

Differential Revision: https://reviews.llvm.org/D28909

llvm-svn: 294461
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 23f8035..c26da03 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -60,7 +60,7 @@
 
 STATISTIC(NumSimplified, "Number of library calls simplified");
 
-static cl::opt<uint64_t> UnfoldElementAtomicMemcpyMaxElements(
+static cl::opt<unsigned> UnfoldElementAtomicMemcpyMaxElements(
     "unfold-element-atomic-memcpy-max-elements",
     cl::init(16),
     cl::desc("Maximum number of elements in atomic memcpy the optimizer is "