[PATCH] Rework DSDT generation in bhyve

[John Baldwin]

While hacking on the power button support, I also started rototilling the DSDT
generation code a bit.  My initial goal was to enumerate the LPC serial ports
(COM1 and COM2) properly via ACPI.  I ended up doing the following:

- Moved the info for the top-level PCI bus into the PCI emulation code and
  added ResourceProducer entries for the memory ranges decoded by the bus
  for memory BARs.
- I added a framework to allow each PCI emulation driver to optionally write
  an entry into the DSDT under the \_SB_.PCI0 namespace.  The LPC driver uses
  this to write a node for the LPC bus (\_SB_.PCI0.ISA).
- I added a linker set to allow any LPC devices to write entries into the
  DSDT below the LPC node.  I moved the existing block for the RTC out of
  acpi.c and into the RTC driver.  I added DSDT nodes for the AT PIC,
  the 8254 ISA timer, and the LPC UART devices.
- I also added a "SuperIO" device under the LPC node to claim "system
  resources" (as is done in real hardware).  I added a linker set to allow
  various drivers to add IO or memory ranges that should be claimed by
  SuperIO and then added the extended RTC IO range and the registers used
  for ACPI power management as system resources.

The end result is that for the stock VM created by vmrun.sh, the attimer0,
uart0, and uart1 devices move from isa0 to acpi0.  There is also a PIC
device that would be claimed by 'device atpic' (but the stock amd64 kernel
doesn't include that).  The DSDT is also a bit more fleshed out, and also
looks "nice" as devices are mostly laid out in the normal tree rather than
using separate Scope() sections for each device.

Note that I did add some helper routines for writing out DSDT lines and
resource entries to try to simplify the code in the various DSDT handlers
and make the code that generates DSDT lines a bit more readable (e.g. the
implicit newlines make things more readable IMO).

The patch is relative to the previous power button patch and is at
http://www.FreeBSD.org/~jhb/patches/bhyve_dsdt.patch

Assuming these are ok, the next thing I might work on is cleaning up
the PCI INTx interrupts.  They should really all be rounted to the I/O APIC
intpins above 15 (and we should leave ISA IRQs 5, 10, and 11 alone in APIC
mode and only fall back to that if we are using the 8259As and a real ELCR).
The MP Table output would need some minor tweaking for that, and for ACPI we
should generate a _PRT table under _SB_.PCI0 in pci_emul.c.

-- 
John Baldwin