linux/modules: ignore checkpatch's MACRO_ARG_UNUSED

Linux's checkpatch now reports some warnings:

    WARNING:MACRO_ARG_UNUSED: Argument 'pud' is not used in function-like macro
    #87: FILE: pagetables.c:87:
    +# define pud_large(pud) false

    WARNING:MACRO_ARG_UNUSED: Argument 'pgd' is not used in function-like macro
    #88: FILE: pagetables.c:88:
    +# define pgd_large(pgd) false

    total: 0 errors, 2 warnings, 1019 lines checked

https://docs.kernel.org/dev-tools/checkpatch.html states that "We
advocate for utilizing static inline functions to replace such macros.".
However this would break the simple compatibility across architectures
and kernel versions of this module.

Silence the warning instead.

linux/modules/Makefile

@@ -87,6 +87,7 @@ checkpatch:
 		--ignore LONG_LINE \
 		--ignore LONG_LINE_COMMENT \
 		--ignore LONG_LINE_STRING \
+		--ignore MACRO_ARG_UNUSED \
 		--ignore REPEATED_WORD
 
 .PHONY: all clean install infos test checkpatch