mb/google/brya/var/osiris: Enable Fast VMode for osiris

Fast VMode nmakes the SoC throttle when the current exceeds the I_TRIP
threshold.

BUG=b:270640775
BRANCH=firmware-brya-14505.B
TEST=Verify that the feature is enabled by reading from fsp log

Change-Id: I35f577e1bab0f8dda10061903df13730e2c8ee04
Signed-off-by: David Wu <david_wu@quanta.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/73243
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Subrata Banik <subratabanik@google.com>
Reviewed-by: Bob Moragues <moragues@chromium.org>
Reviewed-by: Nick Vaccaro <nvaccaro@google.com>

src/mainboard/google/brya/variants/osiris/overridetree.cb

@@ -9,6 +9,10 @@ fw_config
 	end
 end
 chip soc/intel/alderlake
+	register "domain_vr_config[VR_DOMAIN_IA]" = "{
+		.enable_fast_vmode = 1,
+	}"
+
 	register "sagv" = "SaGv_Enabled"
 
 	# As per Intel Advisory doc#723158, the change is required to prevent possible