sh/next: Fix build fail by asm/system.h in asm/bitops.h

sh/next: Fix build fail by asm/system.h in asm/bitops.h

Other files are not done include definitely by asm/system.h made
include in asm/bitops.h.
This patch remove asm/system.h from asm/bitops.h.

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LANG=C make ARCH=sh CROSS_COMPILE=sh4-linux-gnu-
  CHK     include/linux/version.h
  CHK     include/generated/utsrelease.h
make[1]: `include/generated/machtypes.h' is up to date.
  CC      arch/sh/kernel/asm-offsets.s
In file included from include/asm-generic/getorder.h:7,
               from /home/iwamatsu/work/kernel/sh-2.6-devel/arch/sh/include/asm/page.h:187,
               from /home/iwamatsu/work/kernel/sh-2.6-devel/arch/sh/include/asm/mmu.h:38,
               from /home/iwamatsu/work/kernel/sh-2.6-devel/arch/sh/include/asm/system_32.h:5,
               from /home/iwamatsu/work/kernel/sh-2.6-devel/arch/sh/include/asm/system.h:179,
               from /home/iwamatsu/work/kernel/sh-2.6-devel/arch/sh/include/asm/bitops.h:10,
               from include/linux/bitops.h:22,
               from include/linux/thread_info.h:52,
               from include/linux/preempt.h:9,
               from include/linux/spinlock.h:50,
               from include/linux/mmzone.h:7,
               from include/linux/gfp.h:4,
               from include/linux/mm.h:8,
               from arch/sh/kernel/asm-offsets.c:13:
include/linux/log2.h: In function '__ilog2_u32':
include/linux/log2.h:34: error: implicit declaration of function 'fls'
include/linux/log2.h: In function '__ilog2_u64':
include/linux/log2.h:42: error: implicit declaration of function 'fls64'
include/linux/log2.h: In function '__roundup_pow_of_two':
include/linux/log2.h:63: error: implicit declaration of function 'fls_long'
-----

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>