sbp(4): Sync sbp.h with FreeBSD

* Change u_intXX_t to uintXX_t.

* Change a couple of 'unsigned long's to uint32_t where appropriate.

* Define Logical Unit Reset so it can be used in sbp_targ

Obtained-from: FreeBSD
sbp(4): Support MAXPHYS up to 512KB

- We need at least two OCBs with indirect pointers allocated in a 4KB page.
- SBP_MAXPHYS can increase to 1MB once we separate management OCB/ORB
  which usually does not need indirect pointers.
- We have to increase SBP_DMA_SIZE for MAXPHYS larger than 1MB.

Obtained-from: FreeBSD