net-p2p/litecoin: fix build on big-endian architectures

Include sys/endian.h in src/crypto/scrypt.cpp, big-endian architectures need it:
crypto/scrypt.cpp:157:3: error: 'be32enc' was not declared in this scope

157 |   be32enc(ivec, (uint32_t)(i + 1));
    |   ^~~~~~~

crypto/scrypt.cpp: In function 'void scrypt_1024_1_1_256_sp_generic(const char*, char*, char*)':
crypto/scrypt.cpp:269:10: error: 'le32dec' was not declared in this scope

269 |   X[k] = le32dec(&B[4 * k]);
    |          ^~~~~~~

crypto/scrypt.cpp:285:3: error: 'le32enc' was not declared in this scope

285 |   le32enc(&B[4 * k], X[k]);
    |   ^~~~~~~

PR: 240695
Approved by: hsw@bitmark.com (maintainer), linimon (mentor)