arm, ubifs: fix gcc5.x compiler warning

arm, ubifs: fix gcc5.x compiler warning

compiling U-Boot for openrd_base_defconfig with
gcc 5.x shows the following warning:

  CC      fs/ubifs/super.o
In file included from fs/ubifs/ubifs.h:35:0,
                 from fs/ubifs/super.c:37:
fs/ubifs/super.c: In function 'atomic_inc':
./arch/arm/include/asm/atomic.h:55:2: warning: 'flags' is used uninitialized in this function [-Wuninitialized]
  local_irq_save(flags);
  ^
fs/ubifs/super.c: In function 'atomic_dec':
./arch/arm/include/asm/atomic.h:64:2: warning: 'flags' is used uninitialized in this function [-Wuninitialized]
  local_irq_save(flags);
  ^
  CC      fs/ubifs/sb.o
[...]
  CC      fs/ubifs/lpt.o
In file included from include/linux/bitops.h:123:0,
                 from include/common.h:20,
                 from include/ubi_uboot.h:17,
                 from fs/ubifs/ubifs.h:37,
                 from fs/ubifs/lpt.c:35:
fs/ubifs/lpt.c: In function 'test_and_set_bit':
./arch/arm/include/asm/bitops.h:57:2: warning: 'flags' is used uninitialized in this function [-Wuninitialized]
  local_irq_save(flags);
  ^
  CC      fs/ubifs/lpt_commit.o
In file included from include/linux/bitops.h:123:0,
                 from include/common.h:20,
                 from include/ubi_uboot.h:17,
                 from fs/ubifs/ubifs.h:37,
                 from fs/ubifs/lpt_commit.c:26:
fs/ubifs/lpt_commit.c: In function 'test_and_set_bit':
./arch/arm/include/asm/bitops.h:57:2: warning: 'flags' is used uninitialized in this function [-Wuninitialized]
  local_irq_save(flags);
  ^
  CC      fs/ubifs/scan.o
  CC      fs/ubifs/lprops.o
  CC      fs/ubifs/tnc.o
In file included from include/linux/bitops.h:123:0,
                 from include/common.h:20,
                 from include/ubi_uboot.h:17,
                 from fs/ubifs/ubifs.h:37,
                 from fs/ubifs/tnc.c:30:
fs/ubifs/tnc.c: In function 'test_and_set_bit':
./arch/arm/include/asm/bitops.h:57:2: warning: 'flags' is used uninitialized in this function [-Wuninitialized]
  local_irq_save(flags);
  ^
  CC      fs/ubifs/tnc_misc.o

Fix it.

Signed-off-by: Heiko Schocher <hs@denx.de>