mb/google/bluey/var/quartz: Enable PS8820 support

Select MAINBOARD_HAS_PS8820_RETIMER for the Quartz board variant.
Quartz uses external PS8820 retimers that require explicit
configuration to achieve SuperSpeed data rates.

BUG=b:473489095
TEST=Verify USB SS detection on Quartz.

Sample xHCI PORTSC register output:
```
firmware-shell: md 0x0a800420 8
0a800420: 000002a0 00000000 00000000 00000000    ................
0a800430: 00001203 00000000 00000000 00000000    ................
firmware-shell: md 0x0a600420 8
0a600420: 000002a0 00000000 00000000 00000000    ................
0a600430: 00001203 00000000 00000000 00000000    ................
```

Change-Id: Ibb801adc5f7e874a403c644a5c1b3aa592a3d067
Signed-off-by: Kapil Porwal <kapilporwal@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/90712
Reviewed-by: Jayvik Desai <jayvik@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Pranava Y N <pranavayn@google.com>
Reviewed-by: Subrata Banik <subratabanik@google.com>

src/mainboard/google/bluey/Kconfig

@@ -56,6 +56,7 @@ config BOARD_GOOGLE_QUENBIH
 config BOARD_GOOGLE_QUARTZ
 	select BOARD_GOOGLE_MODEL_QUARTZ
 	select SOC_QUALCOMM_HAMOA
+	select MAINBOARD_HAS_PS8820_RETIMER
 	select MAINBOARD_NO_USB_A_PORT
 	select MAINBOARD_SUPPORTS_PARALLEL_CHARGING