Squashed commit upgrading to mbedtls-2.28.1

Squash merging branch import/mbedtls-2.28.1

 ebf1f6a58089 ("libmbedtls: compile new files added with 2.28.1")
 3ffb51b58a54 ("libmbedtls: add SM2 curve")
 c425755720b4 ("libmbedtls: mbedtls_mpi_exp_mod(): optimize mempool usage")
 23493c822a82 ("libmbedtls: mbedtls_mpi_exp_mod(): reduce stack usage")
 dcdca2348dff ("libmbedtls: mbedtls_mpi_exp_mod() initialize W")
 dc2994976958 ("libmbedtls: fix no CRT issue")
 c6628873b281 ("libmbedtls: add interfaces in mbedtls for context memory operation")
 8acd202d3e55 ("libmedtls: mpi_miller_rabin: increase count limit")
 37284e28d5d9 ("libmbedtls: add mbedtls_mpi_init_mempool()")
 b499a75f29f3 ("libmbedtls: make mbedtls_mpi_mont*() available")
 2080a8c96a5d ("mbedtls: configure mbedtls to reach for config")
 e0858334327a ("mbedtls: remove default include/mbedtls/config.h")
 dd9688e6b8ce ("Import mbedtls-2.28.1")

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>
diff --git a/lib/libmbedtls/mbedtls/library/ccm.c b/lib/libmbedtls/mbedtls/library/ccm.c
index 424ee77..a21a37f 100644
--- a/lib/libmbedtls/mbedtls/library/ccm.c
+++ b/lib/libmbedtls/mbedtls/library/ccm.c
@@ -200,7 +200,7 @@
     memcpy( b + 1, iv, iv_len );
 
     for( i = 0, len_left = length; i < q; i++, len_left >>= 8 )
-        b[15-i] = (unsigned char)( len_left & 0xFF );
+        b[15-i] = MBEDTLS_BYTE_0( len_left );
 
     if( len_left > 0 )
         return( MBEDTLS_ERR_CCM_BAD_INPUT );
@@ -221,8 +221,7 @@
         src = add;
 
         memset( b, 0, 16 );
-        b[0] = (unsigned char)( ( add_len >> 8 ) & 0xFF );
-        b[1] = (unsigned char)( ( add_len      ) & 0xFF );
+        MBEDTLS_PUT_UINT16_BE( add_len, b, 0 );
 
         use_len = len_left < 16 - 2 ? len_left : 16 - 2;
         memcpy( b + 2, src, use_len );