tree-wide: drop "static inline" use in .c files

"static inline" makes sense in .h files. But in .c files it's useless
decoration, the compiler should just make its own decisions there, and
it can do that.

hence, replace all remaining uses of "static line" by a simple" static"
in all .c files (but keep them in .h files, where they make sense)

src/basic/efivars.c

@@ -415,7 +415,7 @@ int systemd_efi_options_variable(char **ret) {
         return r;
 }
 
-static inline int compare_stat_mtime(const struct stat *a, const struct stat *b) {
+static int compare_stat_mtime(const struct stat *a, const struct stat *b) {
         return CMP(timespec_load(&a->st_mtim), timespec_load(&b->st_mtim));
 }