libpayload/storage/ahci: Use pacc pointer to read device class

The PCI bus gets already scanned while gathering system information.
Therefore, use the pacc pointer from sysinfo_t to read the device class
of PCI devices instead of rescanning the bus.

Change-Id: I4c79e71777e718f5065107ebf780ca9fdb4f1b0c
Signed-off-by: Felix Singer <felix.singer@secunet.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/46416
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

payloads/libpayload/include/pci/pci.h

@@ -66,6 +66,7 @@
 #define PCI_ROM_ADDRESS1	0x38 // on bridges
 #define PCI_ROM_ADDRESS_MASK	~0x7ff
 
+#define PCI_CLASS_STORAGE_AHCI	0x0106
 #define PCI_CLASS_MEMORY_OTHER	0x0580
 
 #define PCI_VENDOR_ID_INTEL 0x8086