lib: sw842: select crc32

The sw842 library code was merged in linux-4.1 and causes a very rare randconfig
failure when CONFIG_CRC32 is not set:

    lib/built-in.o: In function `sw842_compress':
    oid_registry.c:(.text+0x12ddc): undefined reference to `crc32_be'
    lib/built-in.o: In function `sw842_decompress':
    oid_registry.c:(.text+0x137e4): undefined reference to `crc32_be'

This adds an explict 'select CRC32' statement, similar to what the other users
of the crc32 code have. In practice, CRC32 is always enabled anyway because
over 100 other symbols select it.

Cc: stable@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 2da572c9 ("lib: add software 842 compression/decompression")
Acked-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>