mb/google/hatch/var/kohaku: ensure FPMCU is power cycled on reset

Leakage from the SPI CS line onto the FPMCU VDD rail was preventing
the FPMCU from fully shutting down on AP reset.

Instead of simply turning off the power rail, now ensure the CS
line is not driven high until late in coreboot.

This ensures it is completely off for the requisite minimum of 200ms
(now measured at approx 1100ms).

BUG=b:245953688
TEST=Confirmed FPMCU is still functional on Kohaku.
Confirmed FpRebootPowerCycle unit test now passes
BRANCH=Hatch

Signed-off-by: Tarun Tuli <taruntuli@google.com>
Change-Id: I1e7e32f61c3ac1b3154d42821cc1dd4c5d3de303
Reviewed-on: https://review.coreboot.org/c/coreboot/+/68819
Reviewed-by: Nick Vaccaro <nvaccaro@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/hatch/variants/kohaku/gpio.c

@@ -8,8 +8,6 @@
 static const struct pad_config gpio_table[] = {
 	/* A8  : PEN_GARAGE_DET_L (wake) */
 	PAD_CFG_GPI_SCI(GPP_A8, NONE, DEEP, EDGE_SINGLE, NONE),
-	/* A11 : PCH_SPI_FPMCU_CS_L */
-	PAD_CFG_NF(GPP_A11, NONE, DEEP, NF2),
 	/* A12 : FPMCU_RST_ODL */
 	PAD_CFG_GPO(GPP_A12, 0, DEEP),
 	/* A16 : EMR_GARAGE_DET (notification) */
@@ -130,6 +128,23 @@ const struct pad_config *variant_early_gpio_table(size_t *num)
 	return early_gpio_table;
 }
 
+/* Set the FPMCU SPI CS line very late to workaround
+ * leakage of this line onto the VDD of the MCU.
+ */
+static const struct pad_config finalize_gpio_table[] = {
+	/* A11 : PCH_SPI_FPMCU_CS_L */
+	PAD_CFG_NF(GPP_A11, NONE, DEEP, NF2),
+};
+
+/*
+ * GPIOs configured during the mainboard finalize
+ */
+const struct pad_config *variant_finalize_gpio_table(size_t *num)
+{
+	*num = ARRAY_SIZE(finalize_gpio_table);
+	return finalize_gpio_table;
+}
+
 /*
  * Default GPIO settings before entering non-S5 sleep states.
  * Configure A12: FPMCU_RST_ODL as GPO before entering sleep.

src/mainboard/google/hatch/variants/kohaku/ramstage.c

@@ -5,7 +5,7 @@
 #include <baseboard/variants.h>
 #include <soc/gpio.h>
 
-void variant_ramstage_init(void)
+void variant_final(void)
 {
 	/*
 	 * Enable power to FPMCU, wait for power rail to stabilize,