Move PIT setup from clock.c to hw/timer.c.

Move the hardware setup to the hw/timer.c code.  This eliminates the
need for a separate hw/pit.h file with definitions.

Also, move the IRQ counting code (which is dependent on the BDA) from
hw/timer.c to clock.c.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
Rename hw/cmos.h to hw/rtc.h and copy RTC code from clock.c to hw/rtc.c.

Group the Real Time Clock code into hw/rtc.[ch].

Also, use rtc_read/write/mask function naming (instead of
inb/outb_cmos) to be more consistent with other register accessors.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
Move dma code to new file hw/dma.c.

Move the DMA controller code in resume.c and hw/floppy.c to a new file
hw/dma.c.  This centralizes the DMA controller code into one place.

Also, don't unmask the floppy DRQ during floppy setup - there is no
reason to unmask the DRQ prior to a command being programmed into the
DMA controller.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
Remove ioport.h; disperse its contents to other header files.

Move the inb(), insb(), etc. code from ioport.h to x86.h.  Move the
PORT_* definitions to their appropriate hardware files.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>