Change in coreboot[master]: mb/google/brya/variants/primus: enable RTD3 for PCIe-eMMC bridge

[Tim Wawrzynczak (Code Review)]

Attention is currently required from: Malik Hsu, Zhuohao Lee.
Tim Wawrzynczak has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/59135 )

Change subject: mb/google/brya/variants/primus: enable RTD3 for PCIe-eMMC bridge
......................................................................

Patch Set 4:

(2 comments)

File src/mainboard/google/brya/variants/primus/overridetree.cb:

https://review.coreboot.org/c/coreboot/+/59135/comment/38075b2a_87677276 
PS4, Line 125: device generic 0 on end
suggestion: give this device a name, then see the comment below, this can be made a lot simpler now 😊

`device generic 0 alias emmc_rtd3 on end`

File src/mainboard/google/brya/variants/primus/variant.c:

https://review.coreboot.org/c/coreboot/+/59135/comment/d9f6a53c_158a4485 
PS4, Line 9: extern struct chip_operations soc_intel_common_block_pcie_rtd3_ops;
           : 
           : static void devtree_update_emmc_rtd3(uint32_t board_ver)
           : {
           : 	struct device *rtd3_dev = NULL, *child = NULL;
           : 	struct device *pcie_rp3_dev = pcidev_path_on_root(PCH_DEVFN_PCIE3);
           : 
           : 	if (board_ver > 1)
           : 		return;
           : 
           : 	while ((child = dev_bus_each_child(pcie_rp3_dev->link_list, child)) != NULL) {
           : 		if (child->path.type != DEVICE_PATH_GENERIC)
           : 			continue;
           : 		if (child->path.generic.id != 0)
           : 			continue;
           : 		if (child->chip_ops == &soc_intel_common_block_pcie_rtd3_ops)
           : 			rtd3_dev = child;
           : 	}
           : 	rtd3_dev->enabled = 0;
           : }
This can be made simpler with the name given it from above:

```
DEV_PTR(emmc_rtd3);

static void devtree_update_emmc_rtd3(uint32_t board_ver)
{
    if (board_ver > 1)
    	return;

emmc_rtd3->enabled = 0;
}
```