[SPARC]: Fix bus handling in build_device_resources().

We mistakedly modify 'bus' in the innermost loop.  What
should happen is that at each register index iteration,
we start with the same 'bus'.

So preserve it's value at the top level, and use a loop
local variable 'dbus' for iteration.

This bug causes registers other than the first to be
decoded improperly.

Signed-off-by: David S. Miller <davem@davemloft.net>