Refactored unsigned long negations

Replaced two instances of negating an unsigned long, which was
resulting in aborts from unsigned integer sanitization with the
equivalent logical not-add 1.

Bug: 25884483
Change-Id: Ic7498e0af638dcd438ce69803021d3cdc3acd4f6

libs/minikin/SparseBitSet.cpp

@@ -90,13 +90,13 @@ void SparseBitSet::initFromRanges(const uint32_t* ranges, size_t nRanges) {
         size_t nElements = (end - (start & ~kElMask) + kElMask) >> kLogBitsPerEl;
         if (nElements == 1) {
             mBitmaps[index] |= (kElAllOnes >> (start & kElMask)) &
-                (kElAllOnes << ((-end) & kElMask));
+                (kElAllOnes << ((~end + 1) & kElMask));
         } else {
             mBitmaps[index] |= kElAllOnes >> (start & kElMask);
             for (size_t j = 1; j < nElements - 1; j++) {
                 mBitmaps[index + j] = kElAllOnes;
             }
-            mBitmaps[index + nElements - 1] |= kElAllOnes << ((-end) & kElMask);
+            mBitmaps[index + nElements - 1] |= kElAllOnes << ((~end + 1) & kElMask);
         }
         for (size_t j = startPage + 1; j < endPage + 1; j++) {
             mIndices[j] = (currentPage++) << (kLogValuesPerPage - kLogBitsPerEl);