src/include: Fix typos

Change-Id: I52302e99708bca2f1e5e45f52cacd42e05a5fbd5
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37567
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/include/b64_decode.h

@@ -22,7 +22,7 @@
  *
  * The user provides output buffer of the size guaranteed to fit the result.
  *
- * Returns the size of the decoded data or zero if invalid charactes were
+ * Returns the size of the decoded data or zero if invalid characters were
  * encountered in the input buffer.
  */
 size_t b64_decode(const uint8_t *input_data,