parade/ps8640: Initialize edid_size

decode_edid either gets EDID_LENGTH bytes or (in the extended case),
2*EDID_LENGTH.
See that this is reflected in its size argument.

Change-Id: If6c76358db4e9ee01c2bd2dbdd5948c61b7aa5bc
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: https://review.coreboot.org/14698
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/drivers/parade/ps8640/ps8640.c

@@ -25,7 +25,7 @@ int ps8640_get_edid(uint8_t bus, uint8_t chip, struct edid *out)
 {
 	int ret;
 	u8 edid[EDID_LENGTH * 2];
-	int edid_size;
+	int edid_size = EDID_LENGTH;
 
 	i2c_writeb(bus, chip + 2, PAGE2_I2C_BYPASS,
 		   EDID_I2C_ADDR | I2C_BYPASS_EN);