MIPS: bitops: fix -Wshadow in asm/bitops.h

Solves the following repetitive warning when building with -Wshadow:

In file included from ./include/linux/bitops.h:32,
                 from ./include/linux/kernel.h:11,
                 from ./include/linux/skbuff.h:13,
                 from ./include/linux/if_ether.h:19,
                 from ./include/linux/etherdevice.h:20:
./arch/mips/include/asm/bitops.h: In function ‘test_and_set_bit_lock’:
./arch/mips/include/asm/bitops.h:46:16: warning: declaration of ‘orig’ shadows a previous local [-Wshadow]
   46 |  unsigned long orig, temp;    \
      |                ^~~~
./arch/mips/include/asm/bitops.h:190:10: note: in expansion of macro ‘__test_bit_op’
  190 |   orig = __test_bit_op(*m, "%0",
      |          ^~~~~~~~~~~~~
./arch/mips/include/asm/bitops.h:185:21: note: shadowed declaration is here
  185 |  unsigned long res, orig;
      |                     ^~~~
./arch/mips/include/asm/bitops.h: In function ‘test_and_clear_bit’:
./arch/mips/include/asm/bitops.h:46:16: warning: declaration of ‘orig’ shadows a previous local [-Wshadow]
   46 |  unsigned long orig, temp;    \
      |                ^~~~
./arch/mips/include/asm/bitops.h:236:9: note: in expansion of macro ‘__test_bit_op’
  236 |   res = __test_bit_op(*m, "%1",
      |         ^~~~~~~~~~~~~
./arch/mips/include/asm/bitops.h:229:21: note: shadowed declaration is here
  229 |  unsigned long res, orig;
      |                     ^~~~
./arch/mips/include/asm/bitops.h:46:16: warning: declaration of ‘orig’ shadows a previous local [-Wshadow]
   46 |  unsigned long orig, temp;    \
      |                ^~~~
./arch/mips/include/asm/bitops.h:241:10: note: in expansion of macro ‘__test_bit_op’
  241 |   orig = __test_bit_op(*m, "%0",
      |          ^~~~~~~~~~~~~
./arch/mips/include/asm/bitops.h:229:21: note: shadowed declaration is here
  229 |  unsigned long res, orig;
      |                     ^~~~
./arch/mips/include/asm/bitops.h: In function ‘test_and_change_bit’:
./arch/mips/include/asm/bitops.h:46:16: warning: declaration of ‘orig’ shadows a previous local [-Wshadow]
   46 |  unsigned long orig, temp;    \
      |                ^~~~
./arch/mips/include/asm/bitops.h:273:10: note: in expansion of macro ‘__test_bit_op’
  273 |   orig = __test_bit_op(*m, "%0",
      |          ^~~~~~~~~~~~~
./arch/mips/include/asm/bitops.h:266:21: note: shadowed declaration is here
  266 |  unsigned long res, orig;
      |                     ^~~~

Signed-off-by: Alexander Lobakin <alobakin@pm.me>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>