SED Opal Fixups

So we have a few patches here, they're pretty small. First patch changes
the sed-opal ioctl function parameters to take a void __user* instead of
an unsigned long, this required a small cast in the nvme driver.
Patch 2 is a UAPI fixup for the IOW to make an ioctl
the right size. Patch 3 fixes a compiliation error when building using
KSAN due to the stack frame being too large. And lastly we move the
Maintainers list from nvme to linux-block.