s390: Rename head64.S to head.S

All the code is 64 bit, therefore remove the superfluous suffix.

Reviewed-by: Jens Remus <jremus@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/kernel/Makefile

@@ -36,7 +36,7 @@ CFLAGS_stacktrace.o	+= -fno-optimize-sibling-calls
 CFLAGS_dumpstack.o	+= -fno-optimize-sibling-calls
 CFLAGS_unwind_bc.o	+= -fno-optimize-sibling-calls
 
-obj-y	:= head64.o traps.o time.o process.o early.o setup.o idle.o vtime.o
+obj-y	:= head.o traps.o time.o process.o early.o setup.o idle.o vtime.o
 obj-y	+= processor.o syscall.o ptrace.o signal.o cpcmd.o ebcdic.o nmi.o
 obj-y	+= debug.o irq.o ipl.o dis.o vdso.o cpufeature.o
 obj-y	+= sysinfo.o lgr.o os_info.o ctlreg.o

arch/s390/kernel/setup.c

@@ -110,7 +110,7 @@ struct exception_table_entry __amode31_ref *__stop_amode31_ex_table = _stop_amod
  * Because the AMODE31 sections are relocated below 2G at startup,
  * the content of control registers CR2, CR5 and CR15 must be updated
  * with new addresses after the relocation. The initial initialization of
- * control registers occurs in head64.S and then gets updated again after AMODE31
+ * control registers occurs in head.S and then gets updated again after AMODE31
  * relocation. We must access the relevant AMODE31 tables indirectly via
  * pointers placed in the .amode31.refs linker section. Those pointers get
  * updated automatically during AMODE31 relocation and always contain a valid