lib/crc: remove unnecessary prompt for CONFIG_CRC32 and drop 'default y'

All modules that need CONFIG_CRC32 already select it, so there is no
need to bother users about the option, nor to default it to y.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250401221600.24878-2-ebiggers@kernel.org


Signed-off-by: Eric Biggers <ebiggers@google.com>