Allow the compiler to verify consistency of function declarations and
function definitions. This patch fixes the following sparse errors:

block/blk-crypto-profile.c:241:14: error: no previous prototype for ‘blk_crypto_get_keyslot’ [-Werror=missing-prototypes]
  241 | blk_status_t blk_crypto_get_keyslot(struct blk_crypto_profile *profile,
      |              ^~~~~~~~~~~~~~~~~~~~~~
block/blk-crypto-profile.c:318:6: error: no previous prototype for ‘blk_crypto_put_keyslot’ [-Werror=missing-prototypes]
  318 | void blk_crypto_put_keyslot(struct blk_crypto_keyslot *slot)
      |      ^~~~~~~~~~~~~~~~~~~~~~
block/blk-crypto-profile.c:344:6: error: no previous prototype for ‘__blk_crypto_cfg_supported’ [-Werror=missing-prototypes]
  344 | bool __blk_crypto_cfg_supported(struct blk_crypto_profile *profile,
      |      ^~~~~~~~~~~~~~~~~~~~~~~~~~
block/blk-crypto-profile.c:373:5: error: no previous prototype for ‘__blk_crypto_evict_key’ [-Werror=missing-prototypes]
  373 | int __blk_crypto_evict_key(struct blk_crypto_profile *profile,
      |     ^~~~~~~~~~~~~~~~~~~~~~

Cc: Eric Biggers <ebiggers@google.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20221123172923.434339-1-bvanassche@acm.orgSigned-off-by: Jens Axboe <axboe@kernel.dk>