tpm: Add a proper Kconfig option for crc8 in SPL

The current approach is a bit of a hack and only works for the tpm
subsystem. Add a Kconfig so that crc8 can be enabled in SPL for other
purposes.

Signed-off-by: Simon Glass <sjg@chromium.org>

lib/Kconfig

@@ -422,6 +422,7 @@ config TPM
 config SPL_TPM
 	bool "Trusted Platform Module (TPM) Support in SPL"
 	depends on SPL_DM
+	imply SPL_CRC8
 	help
 	  This enables support for TPMs which can be used to provide security
 	  features for your board. The TPM can be connected via LPC or I2C
@@ -617,6 +618,23 @@ config SPL_MD5
 	  security applications, but it can be useful for providing a quick
 	  checksum of a block of data.
 
+config CRC8
+	def_bool y
+	help
+	  Enables CRC8 support in U-Boot. This is normally required. CRC8 is
+	  a simple and fast checksumming algorithm which does a bytewise
+	  checksum with feedback to produce an 8-bit result. The code is small
+	  and it does not require a lookup table (unlike CRC32).
+
+config SPL_CRC8
+	bool "Support CRC8 in SPL"
+	depends on SPL
+	help
+	  Enables CRC8 support in SPL. This is not normally required. CRC8 is
+	  a simple and fast checksumming algorithm which does a bytewise
+	  checksum with feedback to produce an 8-bit result. The code is small
+	  and it does not require a lookup table (unlike CRC32).
+
 config CRC32
 	def_bool y
 	help

lib/Makefile

@@ -57,12 +57,13 @@ endif
 
 obj-$(CONFIG_$(SPL_TPL_)TPM) += tpm-common.o
 ifeq ($(CONFIG_$(SPL_TPL_)TPM),y)
-obj-y += crc8.o
 obj-$(CONFIG_TPM) += tpm_api.o
 obj-$(CONFIG_TPM_V1) += tpm-v1.o
 obj-$(CONFIG_TPM_V2) += tpm-v2.o
 endif
 
+obj-$(CONFIG_$(SPL_TPL_)CRC8) += crc8.o
+
 obj-y += crypto/
 
 obj-$(CONFIG_$(SPL_TPL_)GENERATE_ACPI_TABLE) += acpi/