nvmet: Export nvmet_update_cc() and nvmet_cc_xxx() helpers

nvmet: Export nvmet_update_cc() and nvmet_cc_xxx() helpers

Make the function nvmet_update_cc() available to target drivers by
exporting it. To also facilitate the manipulation of the cc register
bits, move the inline helper functions nvmet_cc_en(), nvmet_cc_css(),
nvmet_cc_mps(), nvmet_cc_ams(), nvmet_cc_shn(), nvmet_cc_iosqes(), and
nvmet_cc_iocqes() from core.c to nvmet.h so that these functions can be
reused in target controller drivers.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Rick Wertenbroek <rick.wertenbroek@gmail.com>
Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Keith Busch <kbusch@kernel.org>