Convert CONFIG_SPL_HASH_SUPPORT to Kconfig

Move this option to Kconfig and tidy up existing uses.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/T1042RDB_PI_NAND_SECURE_BOOT_defconfig b/configs/T1042RDB_PI_NAND_SECURE_BOOT_defconfig
index 5f6c84b..cbc7083 100644
--- a/configs/T1042RDB_PI_NAND_SECURE_BOOT_defconfig
+++ b/configs/T1042RDB_PI_NAND_SECURE_BOOT_defconfig
@@ -9,6 +9,7 @@
 CONFIG_BOOTDELAY=0
 CONFIG_SPL=y
 CONFIG_SPL_CRYPTO_SUPPORT=y
+CONFIG_SPL_HASH_SUPPORT=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_GREPENV=y
 CONFIG_CMD_MMC=y