Commit 67512a8c ("MIPS: Avoid macro redefinitions") changed how the
MIPS register macros were defined, in order to allow the code to compile
under LLVM/Clang.

The MIPS CRC32 code however wasn't updated accordingly, causing a build
bug when using a MIPS32r6 toolchain without CRC support.

Update the CRC32 code to use the macros correctly, to fix the build
failures.

Fixes: 67512a8c ("MIPS: Avoid macro redefinitions")
Cc: <stable@vger.kernel.org>
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>