Kernel: Assert if rounding-up-to-page-size would wrap around to 0

If we try to align a number above 0xfffff000 to the next multiple of
the page size (4 KiB), it would wrap around to 0. This is most likely
never what we want, so let's assert if that happens.

Kernel/KBufferBuilder.cpp

@@ -42,7 +42,7 @@ inline bool KBufferBuilder::check_expand(size_t size)
     size_t new_buffer_size = m_size + size;
     if (Checked<size_t>::addition_would_overflow(new_buffer_size, 1 * MiB))
         return false;
-    new_buffer_size = PAGE_ROUND_UP(new_buffer_size + 1 * MiB);
+    new_buffer_size = page_round_up(new_buffer_size + 1 * MiB);
     return m_buffer->expand(new_buffer_size);
 }