[IA64] Remove assembler warnings on head.S

This patch removes the following assembler warning messages.

  AS      arch/ia64/kernel/head.o
arch/ia64/kernel/head.S: Assembler messages:
arch/ia64/kernel/head.S:1179: Warning: Use of 'ld8' violates RAW dependency 'CR[PTA]' (data)
arch/ia64/kernel/head.S:1179: Warning: Only the first path encountering the conflict is reported
arch/ia64/kernel/head.S:1178: Warning: This is the location of the conflicting usage
arch/ia64/kernel/head.S:1180: Warning: Use of 'ld8' violates RAW dependency 'CR[PTA]' (data)
arch/ia64/kernel/head.S:1180: Warning: Only the first path encountering the conflict is reported
arch/ia64/kernel/head.S:1178: Warning: This is the location of the conflicting usage
 :
arch/ia64/kernel/head.S:1213: Warning: Use of 'ldf.fill.nta' violates RAW dependency 'CR[PTA]' (data)
arch/ia64/kernel/head.S:1213: Warning: Only the first path encountering the conflict is reported
arch/ia64/kernel/head.S:1178: Warning: This is the location of the conflicting usage

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>