[coreboot] Printing u32 on 32-bit and 64-bit without cast

[Paul Menzel]

Dear coreboot folks,

There is no common length modifier for u32 for “32-bit and 64-bit”. 
Currently, I am running into problems building 
`src/cpu/x86/smm/smm_module_loader.c:415:42` with 
`x86_64-linux-gnu-gcc-10 -m32` [1].

printk(BIOS_DEBUG, "%s: stack_end = 0x%lx\n", __func__, 
stub_params->stack_top - total_stack_size);

Using `PRIx32` fixes the build with 64-bit but now it fails with 32-bit, 
as commit 3a323808 (include, lib: Add <inttypes.h> printf macros) [2] adds

src/include/inttypes.h:#define PRIx32  "x"

which is dependent on the architecture(?), and is not the right length 
modifier for u32 on 32-bit.

Is there an elegant way around it besides casting the values? Do we need 
specific headers for 32-bit or 64-bit?

Kind regards,

Paul

[1]: https://review.coreboot.org/c/coreboot/+/54343
[2]: https://review.coreboot.org/c/coreboot/+/33823