many: more checks for pointer access without NULL check (#41370)

This is a followup for https://github.com/systemd/systemd/pull/41096
that makes more subsystems pass the new `check-pointer-deref` coccinelle
checks. See the individual commits.

My plan is to do a few more of these PRs until we have it all covered. I
could also do it in a single very big PR but I'm worried about a)
conflicts b) that its just too big/annoying to review. Only 7 dirs left
but some (like src/basic) are quite big (~50k loc) so those PRs will be
a bit bigger.

src/boot/initrd.c

@@ -74,7 +74,6 @@ EFI_STATUS initrd_register(
         EFI_HANDLE handle;
         struct initrd_loader *loader;
 
-        POINTER_MAY_BE_NULL(initrd);
         assert(ret_initrd_handle);
 
         /* If no initrd is specified we'll not install any. This avoids registration of the protocol for that