The SB600 RPR documentation does not mention what to do if SATA_BAR0+6

The SB600 RPR documentation does not mention what to do if SATA_BAR0+6
is no longer 0xA0 or 0xB0. It simply assumes that will never happen.
My 500 GB Seagate Barracuda ST3500820AS triggers that corner case on the
first init after poweron.
The current code hangs forever with my drive. Fix this by rerunning the
init sequence after SATA_BAR0+6 is no longer 0xA0 or 0xB0.

Add support for SATA port 2-4 (Primary Slave, Secondary Master,
Secondary Slave).

If only the 2nd SATA port is connected and the hardware acts strangely
(contrary to documentation), it will print the error message below and
continue anyway. The official AMD asm code behaves the same way.
SATA port 0 status = 0
No Primary Master SATA drive on Slot0
SATA port 1 status = 23
0x6=7f, 0x7=7f
drive no longer selected after 0 ms, retrying init
[8 repetitions]
0x6=7f, 0x7=7f
drive no longer selected after 0 ms, retrying init
Primary Slave device is not ready after 10 tries

Activate and improve debug messages for SPEW log level.

Fix some comments.

New log messages look like this:
PCI: 00:12.0 init
sata_bar0=3020
sata_bar1=3060
sata_bar2=3030
sata_bar3=3070
sata_bar4=3000
sata_bar5=fc309000
SATA port 0 status = 23
0x6=a0, 0x7=80
drive detection not yet completed, waiting...
0x6=a0, 0x7=80
drive detection not yet completed, waiting...
[... 281 repetitions ...]
0x6=0, 0x7=50
drive no longer selected after 2820 ms, retrying init
drive detection done after 0 ms
Primary Master device is ready after 2 tries
SATA port 1 status = 23
drive detection done after 0 ms
Primary Slave device is ready after 1 tries
SATA port 2 status = 0
No Secondary Master SATA drive on Slot2
SATA port 3 status = 0
No Secondary Slave SATA drive on Slot3

With this patch, my Asus M2A-VM boots into Linux without problems.

Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Acked-by: Zheng Bao <zheng.bao@amd.com>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@3845 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1