[IA64] Annotate __kernel_syscall_via_epc() with McKinley dispatch info.

Two other very minor changes: use "mov.i" instead of "mov" for reading
ar.pfs (for clarity; doesn't affect the code at all).  Also, predicate
the load of r14 for consistency.

Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>