MIPS: Drop unused positional parameter in local_irq_{dis,en}able

When building with clang's integrated assembler, it points out that the
CONFIG_CPU_HAS_DIEI versions of local_irq_enable and local_irq_disable
have a named parameter that is not used in the body of the macro and it
thinks that $8 is a positional parameter, rather than a register:

  arch/mips/include/asm/asmmacro.h:48:2: warning: macro defined with named parameters which are not used in macro body, possible positional parameter found in body which will have no effect
   .macro local_irq_enable reg=$8
   ^

The comment above the function that performs this check in LLVM notes
that the warning may trigger in this case, even though it is not
problematic. It is easy enough to clean this up by just omitting the
named parameter for this version of the macro, as it is entirely unused.

Reported-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://github.com/ClangBuiltLinux/linux/issues/1415
Link: https://github.com/llvm/llvm-project/commit/81c944cadb7f9e55b3517b7423a820e2577b9279


Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>