lib/raid6: fix unnecessary rebuild of vpermxor*.c

The following four files are every time rebuilt:

  UNROLL  lib/raid6/vpermxor1.c
  UNROLL  lib/raid6/vpermxor2.c
  UNROLL  lib/raid6/vpermxor4.c
  UNROLL  lib/raid6/vpermxor8.c

Fix the suffixes in the targets.

Fixes: 72ad2107 ("lib/raid6: refactor unroll rules with pattern rules")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

lib/raid6/Makefile

@@ -66,7 +66,7 @@ CFLAGS_vpermxor1.o += $(altivec_flags)
 CFLAGS_vpermxor2.o += $(altivec_flags)
 CFLAGS_vpermxor4.o += $(altivec_flags)
 CFLAGS_vpermxor8.o += $(altivec_flags)
-targets += vpermxor1.o vpermxor2.o vpermxor4.o vpermxor8.o
+targets += vpermxor1.c vpermxor2.c vpermxor4.c vpermxor8.c
 $(obj)/vpermxor%.c: $(src)/vpermxor.uc $(src)/unroll.awk FORCE
 	$(call if_changed,unroll)