ia64/pv_ops: move down __kernel_syscall_via_epc.

Move down __kernel_syscall_via_epc to the end of the page.
We want to paravirtualize only __kernel_syscall_via_epc because
it includes privileged instructions. Its paravirtualization increases
its symbols size.

On the other hand, each paravirtualized gate must have e symbols of
same value and size to native's because the page is mapped to GATE_ADDR
and GATE_ADDR + PERCPU_PAGE_SIZE and vmlinux is linked to those symbols.
Later to have the same symbol size, we pads NOPs at the end of
__kernel_syscall_via_epc. Move it after other functions to keep
symbols of other functions have same values and sizes.

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Tony Luck <tony.luck@intel.com>