ec/starlabs/merlin: Don't report a battery capacity higher than design capacity

If B1FC (Battery Full Capacity) is higher than B1DC (Battery Design
Capacity), only report the design capacity. This handles cases where
the battery calibration is incorrect, and the battery runs out before
the OS thinks it's empty.

Signed-off-by: Sean Rhodes <sean@starlabs.systems>
Change-Id: Ib3e4769c809b69e0a237b5f043e6c41c12d53752
Reviewed-on: https://review.coreboot.org/c/coreboot/+/62514
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/ec/starlabs/merlin/acpi/battery.asl

@@ -34,6 +34,9 @@ Device (BAT0)
 	Method (_BIF, 0, Serialized)
 	{
 		BPKG[1] = B1DC
+		If (B1FC >= B1DC) {
+			B1FC = B1DC
+		}
 		BPKG[2] = B1FC
 		BPKG[4] = B1DV
 		If (B1FC)