lib: introduce HASH_CALCULATE option

Build error occurs when CONFIG_EFI_SECURE_BOOT or
CONFIG_EFI_CAPSULE_AUTHENTICATE is enabled,
because hash-checksum.c is not compiled.

Since hash_calculate() implemented in hash-checksum.c can be
commonly used aside from FIT image signature verification,
this commit itroduces HASH_CALCULATE option to decide
if hash-checksum.c shall be compiled.

Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/lib/Makefile b/lib/Makefile
index 6825671..0835ea2 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -61,7 +61,7 @@
 obj-$(CONFIG_$(SPL_)ACPIGEN) += acpi/
 obj-$(CONFIG_$(SPL_)MD5) += md5.o
 obj-$(CONFIG_$(SPL_)RSA) += rsa/
-obj-$(CONFIG_FIT_SIGNATURE) += hash-checksum.o
+obj-$(CONFIG_HASH_CALCULATE) += hash-checksum.o
 obj-$(CONFIG_SHA1) += sha1.o
 obj-$(CONFIG_SHA256) += sha256.o
 obj-$(CONFIG_SHA512_ALGO) += sha512.o