um: define set_pte_at() as a static inline function, not a macro

When defined as macro, the mm argument is unused and subsequently the
variable passed as mm is considered unused by the compiler. This fixes
a build warning.

Signed-off-by: Bartosz Golaszewski <[e-mail]>
Reviewed-by: Geert Uytterhoeven <[e-mail]>
Reviewed-by: Anton Ivanov <[e-mail]>
Acked-by: Anton Ivanov <[e-mail]>
Signed-off-by: Richard Weinberger <[e-mail]>

arch/um/include/asm/pgtable.h

···
 	*pteptr = pte_mknewpage(*pteptr);
 	if(pte_present(*pteptr)) *pteptr = pte_mknewprot(*pteptr);
 }
-#define set_pte_at(mm,addr,ptep,pteval) set_pte(ptep,pteval)
+
+static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
+			      pte_t *pteptr, pte_t pteval)
+{
+	set_pte(pteptr, pteval);
+}
 
 #define __HAVE_ARCH_PTE_SAME
 static inline int pte_same(pte_t pte_a, pte_t pte_b)