sfi: table irq 0xFF means 'no interrupt'

According to the SFI specification irq number 0xFF means device has no
interrupt or interrupt attached via GPIO.

Currently, we don't handle this special case and set irq field in
*_board_info structs to 255.  It leads to confusion in some drivers.
Accelerometer driver tries to register interrupt 255, fails and prints
"Cannot get IRQ" to dmesg.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/platform/mrst/mrst.c

@@ -689,7 +689,9 @@ static int __init sfi_parse_devs(struct sfi_table_header *table)
 			irq_attr.trigger = 1;
 			irq_attr.polarity = 1;
 			io_apic_set_pci_routing(NULL, pentry->irq, &irq_attr);
-		}
+		} else
+			pentry->irq = 0; /* No irq */
+
 		switch (pentry->type) {
 		case SFI_DEV_TYPE_IPC:
 			/* ID as IRQ is a hack that will go away */