lib: Rename rsa-checksum.c to hash-checksum.c

rsa-checksum.c sontains the hash_calculate() implementations. Despite
the "rsa-" file prefix, this function is useful for other algorithms.

To prevent confusion, move this file to lib/, and rename it to
hash-checksum.c, to give it a more "generic" feel.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/rsa/Makefile b/lib/rsa/Makefile
index 8b75d41..c9ac72c 100644
--- a/lib/rsa/Makefile
+++ b/lib/rsa/Makefile
@@ -5,6 +5,6 @@
 # (C) Copyright 2000-2007
 # Wolfgang Denk, DENX Software Engineering, wd@denx.de.
 
-obj-$(CONFIG_$(SPL_TPL_)RSA_VERIFY) += rsa-verify.o rsa-checksum.o
+obj-$(CONFIG_$(SPL_TPL_)RSA_VERIFY) += rsa-verify.o
 obj-$(CONFIG_$(SPL_TPL_)RSA_VERIFY_WITH_PKEY) += rsa-keyprop.o
 obj-$(CONFIG_RSA_SOFTWARE_EXP) += rsa-mod-exp.o