scsi: libsas: Switch back to original event notifiers API

libsas event notifiers required an extension where gfp_t flags must be
explicitly passed. For bisectability, a temporary _gfp() variant of such
functions were added. All call sites then got converted use the _gfp()
variants and explicitly pass GFP context. Having no callers left, the
original libsas notifiers were then modified to accept gfp_t flags by
default.

Switch back to the original event notifiers API, while still passing GFP
context.  The _gfp() notifier variants will be removed afterwards.

Link: https://lore.kernel.org/r/20210118100955.1761652-17-a.darwish@linutronix.de
Cc: Jason Yan <yanaijie@huawei.com>
Reviewed-by: John Garry <john.garry@huawei.com>
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>