mb/google/rex: Redirect AP UART over LPSS UART 0

This patch ensures AP UART messages are coming over LPSS UART 0 hence,
select required kconfig and program both early and late UART
RX/TX GPIOs accroding to the rex schematics dated 06/27.

BUG=b:224325352
TEST=Able to see AP UART log over LPSS UART0.

Signed-off-by: Subrata Banik <subratabanik@google.com>
Change-Id: I7daa8200d1a7cf825dfdfed538573efd57ab2d97
Reviewed-on: https://review.coreboot.org/c/coreboot/+/65454
Reviewed-by: Tarun Tuli <taruntuli@google.com>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/mainboard/google/rex/Kconfig b/src/mainboard/google/rex/Kconfig
index 9e02dd8..98870de 100644
--- a/src/mainboard/google/rex/Kconfig
+++ b/src/mainboard/google/rex/Kconfig
@@ -3,6 +3,7 @@
 	select BOARD_ROMSIZE_KB_32768
 	select HAVE_ACPI_RESUME
 	select HAVE_ACPI_TABLES
+	select INTEL_LPSS_UART_FOR_CONSOLE
 
 config BOARD_GOOGLE_BASEBOARD_REX
 	def_bool n
diff --git a/src/mainboard/google/rex/variants/baseboard/rex/gpio.c b/src/mainboard/google/rex/variants/baseboard/rex/gpio.c
index 8efb7ab..70f05c4 100644
--- a/src/mainboard/google/rex/variants/baseboard/rex/gpio.c
+++ b/src/mainboard/google/rex/variants/baseboard/rex/gpio.c
@@ -7,11 +7,19 @@
 /* Pad configuration in ramstage */
 static const struct pad_config gpio_table[] = {
 	/* ToDo: Fill gpio configuration */
+	/* H8 : UART0_RXD ==> UART_DBG_TX_SOC_RX */
+	PAD_CFG_NF(GPP_H8, NONE, DEEP, NF1),
+	/* H9 : UART0_TXD ==> UART_DBG_RX_SOC_TX */
+	PAD_CFG_NF(GPP_H9, NONE, DEEP, NF1),
 };
 
 /* Early pad configuration in bootblock */
 static const struct pad_config early_gpio_table[] = {
 	/* ToDo: Fill early gpio configuration */
+	/* H8 : UART0_RXD ==> UART_DBG_TX_SOC_RX */
+	PAD_CFG_NF(GPP_H8, NONE, DEEP, NF1),
+	/* H9 : UART0_TXD ==> UART_DBG_RX_SOC_TX */
+	PAD_CFG_NF(GPP_H9, NONE, DEEP, NF1),
 };
 
 const struct pad_config *__weak variant_gpio_table(size_t *num)