ia64: move the ROOT_DEV setup to common code

I'm not sure how useful a platform default ROOT_DEV is these days,
but it pretty sure isn't machvec dependent.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lkml.kernel.org/r/20190813072514.23299-25-hch@lst.de
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/kernel/setup.c

@@ -30,6 +30,7 @@
 #include <linux/console.h>
 #include <linux/delay.h>
 #include <linux/cpu.h>
+#include <linux/kdev_t.h>
 #include <linux/kernel.h>
 #include <linux/memblock.h>
 #include <linux/reboot.h>
@@ -41,6 +42,7 @@
 #include <linux/threads.h>
 #include <linux/screen_info.h>
 #include <linux/dmi.h>
+#include <linux/root_dev.h>
 #include <linux/serial.h>
 #include <linux/serial_core.h>
 #include <linux/efi.h>
@@ -599,6 +601,13 @@ setup_arch (char **cmdline_p)
 	if (!nomca)
 		ia64_mca_init();
 
+	/*
+	 * Default to /dev/sda2.  This assumes that the EFI partition
+	 * is physical disk 1 partition 1 and the Linux root disk is
+	 * physical disk 1 partition 2.
+	 */
+	ROOT_DEV = Root_SDA2;		/* default to second partition on first drive */
+
 	platform_setup(cmdline_p);
 	paging_init();