Style and minor changes:

• Merge esp_sbus.c rev. 1.31 from NetBSD: nuke trailing whitespace. Rev. 1.28 and 1.30 were already merged, 1.29 is not relevant for FreeBSD.
• Remove unused headers.
• Use BUS_PROBE_DEFAULT.
• Use func instead of hardcoded function names in error messages.
• Correct some comments.
• Correct some function declarations to match their prototypes.
• Some style(9) fixes (don't use function calls in initializers; indentation).
• Zero the allocated structs to avoid problems with uninitialized members.
• Remove the ifdef'ed out SBus interrupt priority code and the hook for ncr53c9x_reset(), remove the unused SBus interrupt priority member from esp_softc. On FreeBSD setting the SBus interrupt priority is entirely done in sbus(4) and the reset function isn't even really used in NetBSD.
• s,dma,DMA, in comments.
• Make the code fit in 80 columns.