QCryptographicHashPrivate: standardize on quint8

So we don't have to do these reinterpret_cast everywhere, as most of the
APIs we're calling take unsigned chars themselves. The reinterpret_casts
will be removed in the next commit, which needs to modify those lines
anyway.

Change-Id: Ide4dbd0777a44ed0870efffd17394f9f25062122
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
(cherry picked from commit 2d7a27b918ff576dbd8ec8b3aecaa45f8c78fa5e)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/tools/qcryptographichash.cpp

@@ -191,12 +191,11 @@ public:
     void sha3Finish(int bitCount, Sha3Variant sha3Variant);
 #endif
     class SmallByteArray {
-        std::array<char, MaxHashLength> m_data;
+        std::array<quint8, MaxHashLength> m_data;
         static_assert(MaxHashLength <= std::numeric_limits<std::uint8_t>::max());
-        std::uint8_t m_size;
+        quint8 m_size;
     public:
-        char *data() noexcept { return m_data.data(); }
-        const char *data() const noexcept { return m_data.data(); }
+        quint8 *data() noexcept { return m_data.data(); }
         qsizetype size() const noexcept { return qsizetype{m_size}; }
         bool isEmpty() const noexcept { return size() == 0; }
         void clear() noexcept { m_size = 0; }
@@ -206,7 +205,7 @@ public:
             m_size = std::uint8_t(s);
         }
         QByteArrayView toByteArrayView() const noexcept
-        { return QByteArrayView{data(), size()}; }
+        { return QByteArrayView{m_data.data(), size()}; }
     };
     SmallByteArray result;
 };