Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Make sparc64 compatible with NEW_PCIB and enable it:
- Implement bus_adjust_resource() methods as far as necessary and in non-PCI
bridge drivers as far as feasible without rototilling them.
- As NEW_PCIB does a layering violation by activating resources at layers
above pci(4) without previously bubbling up their allocation there, move
the assignment of bus tags and handles from the bus_alloc_resource() to
the bus_activate_resource() methods like at least the other NEW_PCIB
enabled architectures do. This is somewhat unfortunate as previously
sparc64 (ab)used resource activation to indicate whether SYS_RES_MEMORY
resources should be mapped into KVA, which is only necessary if their
going to be accessed via the pointer returned from rman_get_virtual() but
not for bus_space(9) as the later always uses physical access on sparc64.
Besides wasting KVA if we always map in SYS_RES_MEMORY resources, a driver
also may deliberately not map them in if the firmware already has done so,
possibly in a special way. So in order to still allow a driver to decide
whether a SYS_RES_MEMORY resource should be mapped into KVA we let it
indicate that by calling bus_space_map(9) with BUS_SPACE_MAP_LINEAR as
actually documented in the bus_space(9) page. This is implemented by
allocating a separate bus tag per SYS_RES_MEMORY resource and passing the
resource via the previously unused bus tag cookie so we later on can call
rman_set_virtual() in sparc64_bus_mem_map(). As a side effect this now
also allows to actually indicate that a SYS_RES_MEMORY resource should be
mapped in as cacheable and/or read-only via BUS_SPACE_MAP_CACHEABLE and
BUS_SPACE_MAP_READONLY respectively.
- Do some minor cleanup like taking advantage of rman_init_from_resource(),
factor out the common part of bus tag allocation into a newly added
sparc64_alloc_bus_tag(), hook up some missing newbus methods and replace
some homegrown versions with the generic counterparts etc.
- While at it, let apb_attach() (which can't use the generic NEW_PCIB code
as APB bridges just don't have the base and limit registers implemented)
regarding the config space registers cached in pcib_softc and the SYSCTL
reporting nodes set up.

- Use bus_{read,write}_*(9) instead of bus_space_{read,write}_*(9) etc
and take advantage of rman_get_rid(9) in order to save some softc
members.
- Provide and consume module dependency information for lebuffer(4).

Add front-ends for the 'lebuffer' variants found on some SBus cards.
These are shared-memory variants based on Am79C90-compatible chips
that apart from the missing DMA engine are similar to the 'ledma'
variant including using a (pseudo-)bus/device for the buffer that
the actual LANCE device hangs off from. The performance of these is
close to that of the 'ledma' one, like expected at a few times the
CPU load though.