Remove duplication of table_compute_checksum function

It seems like there was some merge error when first cleaning up and
sharing this function.  We have both an inline version of the function
in include/tables_csum.h and a non-inline version in lib/tables_csum.c.
Rework things so that we only have the non-inline version (due to number
of calls, we should not inline this).

Fixes: 1befb38b8682 ("x86: Move table csum into separate file")
Fixes: 2b445e4d3194 ("x86: Move table csum into separate header")
Cc: Alexander Graf <agraf@csgraf.de>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/include/tables_csum.h b/include/tables_csum.h
index 5f7edc4..4812333 100644
--- a/include/tables_csum.h
+++ b/include/tables_csum.h
@@ -6,16 +6,17 @@
 #ifndef _TABLES_CSUM_H_
 #define _TABLES_CSUM_H_
 
-static inline u8 table_compute_checksum(void *v, int len)
-{
-	u8 *bytes = v;
-	u8 checksum = 0;
-	int i;
-
-	for (i = 0; i < len; i++)
-		checksum -= bytes[i];
-
-	return checksum;
-}
+/**
+ * table_compute_checksum() - Compute a table checksum
+ *
+ * This computes an 8-bit checksum for the configuration table.
+ * All bytes in the configuration table, including checksum itself and
+ * reserved bytes must add up to zero.
+ *
+ * @v:		configuration table base address
+ * @len:	configuration table size
+ * @return:	the 8-bit checksum
+ */
+u8 table_compute_checksum(void *v, int len);
 
 #endif