[IA64] kexec: Repining for EFI RID

[IA64] kexec: Repining for EFI RID

A cut down version of set_one_rr (and ia64_new_rr7) for
use when switching to the EFI RID for SAL, PAL and EFI calls.

There seems to be no need to repin: palcode, mapped_regs or vhpt in this
case. If it turns they do need to be repinned then special care needs to
betaken to track the correct value to repin.  That is generally the values
that were most recently pinned by ia64_new_rr7.

ia64_new_rr7_efi can probably be merged with ia64_new_rr7,
as they are quite similar, but for testing purposes it seems
easier to keep them separate.

Cc: Isaku Yamahata <yamahata@valinux.co.jp>
Cc: Alex Williamson <alex.williamson@hp.com>
Cc: Aron Griffis <aron@hp.com>
Signed-off-by: Simon Horman <horms@verge.net.au>