sstables: remove duplicated code in data_consume_rows_context CELL_VALUE_BYTES
sstables: remove duplicated code in data_consume_rows_context CELL_VALUE_BYTES

Signed-off-by: Benny Halevy <23c997c90eb8537635e9392d48e7af1bf1b2ca22@scylladb.com>

scylladb/scylla,avikivity/scylla,avikivity/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla