Simplify code
Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
diff --git a/library/bignum_core.h b/library/bignum_core.h
index 117c3c5..397f79a 100644
--- a/library/bignum_core.h
+++ b/library/bignum_core.h
@@ -85,8 +85,10 @@
* most significant zero bytes in the input).
*
* \param X The address of the MPI.
+ * May only be #NULL if \nx is 0 and \p buflen is 0.
* \param nx The number of limbs of \p X.
* \param buf The input buffer to import from.
+ * May only be #NULL if \p buflen is 0.
* \param buflen The length in bytes of \p buf.
*
* \return \c 0 if successful.