[S] Change in coreboot[main]: sb/intel/bd82x6x: Improve SLCAP

[Kyösti Mälkki (Code Review)]

Attention is currently required from: Patrick Rudolph.

Kyösti Mälkki has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/78228?usp=email )

Change subject: sb/intel/bd82x6x: Improve SLCAP
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Patch Set 1:

(2 comments)

File src/southbridge/intel/bd82x6x/pch.h:

https://review.coreboot.org/c/coreboot/+/78228/comment/343a5deb_c24a22e2 :
PS1, Line 90: #define D28Fx_SLCAP		0x54
```
#define PCI_EXP_SLTCAP		20	/* Slot Capabilities */
```

File src/southbridge/intel/bd82x6x/pcie.c:

https://review.coreboot.org/c/coreboot/+/78228/comment/42c2876a_14f0e31e :
PS1, Line 141: 	reg32 = pci_read_config32(dev, D28Fx_SLCAP);
Probably should utilise and extend ones from pci_def.h here.

```
#define PCI_EXP_SLTCAP		20	/* Slot Capabilities */
#define  PCI_EXP_SLTCAP_HPC	0x0040	/* Hot-Plug Capable */
#define  PCI_EXP_SLTCAP_PSN	0xfff80000 /* Physical Slot Number */
```