iwlwifi: trans: turn set_pmi into an optional callback
iwlwifi: trans: turn set_pmi into an optional callback

It is not currently implemented for SDIO, and not required for other slave
buses as well.

Signed-off-by: Arik Nemtsov <1a5d131848a166677cc209f94fa988cee9378c32@wizery.com>
Signed-off-by: Emmanuel Grumbach <643a80aaf16a8332d6a70921c14d4bb265446494@intel.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs