common: Move Is4KBAligned() to alignment.h

Aligning on 4KB pages isn't a Switch-specific thing, so this can be
moved to common so it can be used with other things as well.

src/common/alignment.h

@@ -19,4 +19,10 @@ constexpr T AlignDown(T value, std::size_t size) {
     return static_cast<T>(value - value % size);
 }
 
+template <typename T>
+constexpr bool Is4KBAligned(T value) {
+    static_assert(std::is_unsigned_v<T>, "T must be an unsigned value.");
+    return (value & 0xFFF) == 0;
+}
+
 } // namespace Common