soc/amd/picasso: Move sd_emmc_config into emmc_config struct

I plan on adding another eMMC parameter. This refactor keeps the config
contained in a single struct.

BUG=b:159823235
TEST=Build test

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: I4b57d651ab44d6c1cad661d620bffd4207dfebd4
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45095
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
diff --git a/src/mainboard/google/zork/variants/baseboard/devicetree_dalboz.cb b/src/mainboard/google/zork/variants/baseboard/devicetree_dalboz.cb
index a0f6636..4004243 100644
--- a/src/mainboard/google/zork/variants/baseboard/devicetree_dalboz.cb
+++ b/src/mainboard/google/zork/variants/baseboard/devicetree_dalboz.cb
@@ -40,7 +40,9 @@
 
 	# End : OPN Performance Configuration
 
-	register "sd_emmc_config" = "SD_EMMC_EMMC_HS400"
+	register "emmc_config" = "{
+		.timing = SD_EMMC_EMMC_HS400,
+	}"
 
 	register "xhci0_force_gen1" = "0"