[IA64] Ensure that machvec is set up takes place before serial console

Parse the machvec command line option outside of the early_param()
so that ia64_mv is set before any console intialisation that
may result from early_param parsing.

Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Tony Luck <tony.luck@intel.com>