[SERIAL] HCDP IRQ fixup

Some pre-production firmware has incorrect GSI values in the
HCDP, which tells us where the serial console port is, so we
have to do the auto-IRQ thing after all.

drivers/serial/8250_hcdp.c

@@ -186,6 +186,8 @@ setup_serial_hcdp(void *tablep)
 		port.irq = gsi;
 #endif
 		port.flags = UPF_SKIP_TEST | UPF_BOOT_AUTOCONF | UPF_RESOURCES;
+		if (gsi)
+			port.flags |= UPF_AUTO_IRQ;
 
 		/*
 		 * Note: the above memset() initializes port.line to 0,