fix ecc_set_key - no check of private key input buffer size

[karel-m]

When trying to load the following EC / DER key (generated by openssl):

3081be
   0201 01
   0415 00c78b055db0706fd86b5a15e14b9e51f0043d18f9
   a074
      3072
         0201 01
         3020
            0607 2a8648ce3d0101
            0215 00fffffffffffffffffffffffffffffffeffffac73
            3006
              0401 00
              0401 07
            0429 043b4c382ce37aa192a4019e763036f4f5dd4d7ebb938cf935318fdced6bc28286531733c3f03c4fee
            0215 0100000000000000000001b8fa16dfab9aca16b6b3
            0201 01
   a12c
      032a 00040ca9f03d79907c97538177a3027970abefa351073a73120e1b5d2dab02dde37c118a44f8cb267b56

I have found out that the private key:

• 0415 = LTC_ASN1_RAW_BIT_STRING
• value 00c78b055db0706fd86b5a15e14b9e51f0043d18f9 (21 bytes)

is for some reason 1 byte longer (21 bytes) than the curve size (20 bytes).

Therefore I have removed the test inlen <= key->dp.size (not sure if this is not too relaxed, perhaps we can check whether key->k < prime or something like that)