nvmet-auth: select the intended CRYPTO_DH_RFC7919_GROUPS

Commit 71ebe3842ebe ("nvmet-auth: Diffie-Hellman key exchange support")
intends to select 'Support for RFC 7919 FFDHE group parameters' for using
FFDHE groups for NVMe In-Band Authentication.

It however selects CRYPTO_DH_GROUPS_RFC7919, instead of the intended
CRYPTO_DH_RFC7919_GROUPS; notice the swapping of words here.

Correct the select to the intended config option.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>