purism/librem_skl: Enable TPM support

Change the GPIO to match the TPM-enabled motherboards, and add TPM
support in devicetree and enable the config.
After changing the GPIO table, the librem 13v2 and librem 15v3 now
have the same GPIOs, so use a single gpio.h file instead of one
file per variant.

Change-Id: I425654c1c972118aa81c27961246238c2eef782d
Signed-off-by: Youness Alaoui <youness.alaoui@puri.sm>
Reviewed-on: https://review.coreboot.org/23683
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
diff --git a/src/mainboard/purism/librem_skl/Kconfig b/src/mainboard/purism/librem_skl/Kconfig
index f68fd23..be4b7a3 100644
--- a/src/mainboard/purism/librem_skl/Kconfig
+++ b/src/mainboard/purism/librem_skl/Kconfig
@@ -9,6 +9,7 @@
 	select SERIRQ_CONTINUOUS_MODE
 	select MAINBOARD_USES_FSP2_0
 	select SPD_READ_BY_WORD
+	select MAINBOARD_HAS_LPC_TPM
 
 if BOARD_PURISM_BASEBOARD_LIBREM_SKL