Pull up following revision(s) (requested by jdolecek in ticket #841):

sys/dev/isa/isadmareg.h: revision 1.9
sys/dev/isa/isareg.h: revision 1.10
sys/dev/isa/isadma.c: revision 1.67

fix off-by-one in the mapping of the ISA DMA page registers, they actually
start at 0x81; the code used bus_space_map() starting from 0x80 but
used +1 offset for actual I/O, now it maps starting 0x81 and does I/O
without offset

the reads and writes work exactly the same as before, but this frees
0x80 for being mapped independantly
patch provided in PR kern/52468 by Jonathan Chapman; checked against the spec
and also FreeBSD sys/x86/isa/isa_dma.c

(martin)