ia64: move the screen_info setup to common code

There is nothing really platform specific about setting about the
screen_info from the ia64_boot_param structure, so move it from the
dig machvec to common code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lkml.kernel.org/r/20190813072514.23299-26-hch@lst.de


Signed-off-by: Tony Luck <tony.luck@intel.com>