The k_stack data type cannot be u32_t on a 64-bit system as it is
often used to store pointers. Let's define a dedicated type for stack
data values, namely stack_data_t, which can be adjusted accordingly.
For now it is defined to uintptr_t which is the integer type large
enough to hold a pointer, meaning it is equivalent to u32_t on 32-bit
systems and u64_t on 64-bit systems.
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
3d51f7c266