mb/amd/mandolin: change EFS SPI mode from 1-4-4 to 1-1-4

With this change the flash addresses will only get transferred over one
data pin like in the non-quad SPI mode and only the data will get sent
over all four data pins. Since this gives the flash chip a bit more time
to fetch the data the host requested, this allows higher SPI frequencies
resulting in a higher throughput when bigger chunks of memory get read.

BRANCH=zork

Change-Id: Iad4c922ffcdba4b17e6e81244ff37302eb171d97
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45831
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/amd/mandolin/Kconfig

@@ -110,7 +110,7 @@ config VGA_BIOS_DGPU_FILE
 config EFS_SPI_READ_MODE
 	int
 	default 0 if EM100
-	default 5
+	default 3
 
 config EFS_SPI_SPEED
 	int