tls: get rid of constant-time add/sub operations

function                                             old     new   delta
sp_256_sub_10                                          -      22     +22
static.sp_256_mont_reduce_10                         176     178      +2
sp_256_mod_mul_norm_10                              1440    1439      -1
sp_256_proj_point_dbl_10                             453     446      -7
sp_256_ecc_mulmod_10                                1229    1216     -13
static.sp_256_mont_sub_10                             52      30     -22
static.sp_256_cond_sub_10                             32       -     -32
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 1/4 up/down: 24/-75)            Total: -51 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
1 file changed