[L] Change in coreboot[main]: soc/intel/xeon_sp: Share save_dimm_info among Xeon-SP SoCs

[Angel Pons (Code Review)]

Attention is currently required from: Arthur Heymans, Christian Walter, Jincheng Li, Johnny Lin, Jonathan Zhang, Lean Sheng Tan, Patrick Rudolph, Shuo Liu, Tim Chu.

Angel Pons has posted comments on this change by Shuo Liu. ( https://review.coreboot.org/c/coreboot/+/83325?usp=email )

Change subject: soc/intel/xeon_sp: Share save_dimm_info among Xeon-SP SoCs
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Patch Set 3:

(5 comments)

File src/soc/intel/xeon_sp/cpx/romstage.c:

https://review.coreboot.org/c/coreboot/+/83325/comment/cfcb05bf_3b26dede?usp... :
PS3, Line 126: MEMORY_TYPE_DDR4
Note to self: it's equivalent `MEMORY_TYPE_DDR4 = 0x1a`

File src/soc/intel/xeon_sp/gnr/romstage.c:

https://review.coreboot.org/c/coreboot/+/83325/comment/b7afc921_8dfdf134?usp... :
PS3, Line 90: uint8_t get_dram_type(void)
            : {
            : 	const struct SystemMemoryMapHob *hob = get_system_memory_map();
            : 	if (hob && hob->DramType == SPD_MEMORY_TYPE_DDR5_SDRAM)
The code that has been factored out (made shared) uses `struct SystemMemoryMapHob` already. So, instead of getting it here, why not do:

```suggestion
uint8_t get_dram_type(const struct SystemMemoryMapHob *hob)
{
    if (hob->DramType == SPD_MEMORY_TYPE_DDR5_SDRAM)
```

I intentionally removed the NULL check: `save_dimm_info()` already checks that the pointer is non-NULL.

File src/soc/intel/xeon_sp/romstage.c:

https://review.coreboot.org/c/coreboot/+/83325/comment/09fbdc56_b1680f28?usp... :
PS3, Line 43: #if CONFIG(SOC_INTEL_SKYLAKE_SP)
Hmmm, instead of this, why not place `save_dimm_info()` in a separate `dimm_info.c` file, and compile it only for platforms that use it?

https://review.coreboot.org/c/coreboot/+/83325/comment/56e8081e_c50c18d7?usp... :
PS3, Line 69: 
            : 	for (int skt = 0; skt < CONFIG_MAX_SOCKET; skt++) {
            : 		for (int ch = 0; ch < MAX_CH; ch++) {
            : 			for (int dimm = 0; dimm < get_max_dimm_count(); dimm++) {
nit: if `get_max_dimm_count()` always returns the same value, I would add a helper constant:

```suggestion
    const int max_dimm_count = get_max_dimm_count();
    int dimm_num = 0;
    for (int skt = 0; skt < CONFIG_MAX_SOCKET; skt++) {
    	for (int ch = 0; ch < MAX_CH; ch++) {
    		for (int dimm = 0; dimm < max_dimm_count; dimm++) {
```

File src/soc/intel/xeon_sp/spr/romstage.c:

https://review.coreboot.org/c/coreboot/+/83325/comment/7a821cc4_e41bf4a9?usp... :
PS3, Line 132: uint32_t get_max_capacity_mib(void)
Move this next to the other functions?