[M] Change in coreboot[main]: soc/mediatek/mt8196: Add pi_img loader in ramstage

[Yu-Ping Wu (Code Review)]

Attention is currently required from: Hung-Te Lin, Jarried Lin, Yidi Lin.

Yu-Ping Wu has posted comments on this change by Jarried Lin. ( https://review.coreboot.org/c/coreboot/+/86161?usp=email )

Change subject: soc/mediatek/mt8196: Add pi_img loader in ramstage
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Patch Set 1:

(6 comments)

File src/soc/mediatek/mt8196/Kconfig:

https://review.coreboot.org/c/coreboot/+/86161/comment/743c48ac_220a631d?usp... :
PS1, Line 66: config PI_IMG_FIRMWARE
sort

File src/soc/mediatek/mt8196/Makefile.mk:

https://review.coreboot.org/c/coreboot/+/86161/comment/ec0d149a_f4cd0063?usp... :
PS1, Line 103: 	$(CONFIG_PI_IMG_FIRMWARE)
sort

File src/soc/mediatek/mt8196/include/soc/pi_image.h:

https://review.coreboot.org/c/coreboot/+/86161/comment/6ed2ed5b_d86acf7e?usp... :
PS1, Line 9: #define CSRAM_SIZE		(16 * KiB)
           : #define CSRAM_START_ADDR	0x00120000
```
#define PI_IMAGE_CSRAM   <TABS>       0x00120000
#define PI_IMAGE_CSRAM_SIZE   <TABS>  (16 * KiB)
```

File src/soc/mediatek/mt8196/pi_image.c:

https://review.coreboot.org/c/coreboot/+/86161/comment/08f7e005_6ebcabc2?usp... :
PS1, Line 15: struct mtk_mcu *pi_image_load(void)
I'd prefer returning buffer and size directly, without using mtk_mcu.

```
size_t pi_image_load(void **buffer)
{
    *buffer = NULL;
    ...
    *buffer = pi_image.load_buffer;
    return pi_image.run_size;
}
```

File src/soc/mediatek/mt8196/soc.c:

https://review.coreboot.org/c/coreboot/+/86161/comment/9f19cd28_7d819fbb?usp... :
PS1, Line 40: struct mtk_mcu *pi = pi_image_load();
            : 
            : 	void *pi_image = pi->load_buffer;
            : 	size_t pi_image_size = pi->run_size;
Following the other comment above, this would be

```
void *pi_image;
size_t pi_image_size;

pi_image_size = pi_image_load(&pi_image);
```

https://review.coreboot.org/c/coreboot/+/86161/comment/814eb271_3eb91a50?usp... :
PS1, Line 57: pi_image_prepare
How about `add_pi_image_params`