Use uintptr_t instead of unsigned long for pointers.

The sense_ptr thing is quite broken. As near as I can tell, the
driver tries to copyout to a physical address rather than whatever
user address the sense buffer should be copied to. It is not
immediately obvious what user address the sense buffer should be
copied to.

Reviewed by: imp
Obtained from: CheriBSD
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D27578