drivers/*/tpm: Add postcar target

Now postcar is a standalone stage, add
it as target to all TPM bus drivers.
This is a required for a measured boot.

Change-Id: I758185daf3941a29883c2256b900360e112275e1
Signed-off-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>
Reviewed-on: https://review.coreboot.org/29546
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/drivers/spi/tpm/Makefile.inc

@@ -2,3 +2,4 @@ bootblock-$(CONFIG_SPI_TPM) += tis.c tpm.c
 verstage-$(CONFIG_SPI_TPM) += tis.c tpm.c
 romstage-$(CONFIG_SPI_TPM) += tis.c tpm.c
 ramstage-$(CONFIG_SPI_TPM) += tis.c tpm.c
+postcar-$(CONFIG_SPI_TPM) += tis.c tpm.c