bcachefs: Fix bch2_read_retry_nodecode()

BCH_READ_NODECODE mode - used by the move paths - really wants to use
only the original rbio, but the retry path really wants to clone - oof.

Make sure to copy the crc of the pointer we read from back to the
original rbio, or we'll see spurious checksum errors later.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>