Change the range syntax that is giving ctest problems

`ctest` is iffy about whether or not it accepts `..=` syntax, and I
can't figure out what makes it decide whether or not to accept it and
sometimes random changes seem to make things fail, so just replace the
syntax.

This is simpler anyway, and closer matches the upstream definition [1].

Link: https://github.com/torvalds/linux/blob/80e54e84911a923c40d7bee33a34c1b4be148d7a/Makefile#L1316 [1]

(backport <rust-lang#4311>)
(cherry picked from commit 1779f14)

Author: tgross35

libc-test/test/linux_kernel_version.rs

@@ -1,15 +1,16 @@
 //! Compare libc's KERNEL_VERSION macro against a specific kernel version.
 
-#[cfg(
-    target_os = "linux",
-)]
+#[cfg(target_os = "linux")]
 mod t {
     use libc;
 
     #[test]
     fn test_kernel_version() {
-        unsafe {
-            assert_eq!(libc::KERNEL_VERSION(6, 0, 0), 393216);
-        }
+        assert_eq!(unsafe { libc::KERNEL_VERSION(6, 0, 0) }, 393216);
+        // Check that the patch level saturates
+        assert_eq!(unsafe { libc::KERNEL_VERSION(6, 0, 255) }, 393471);
+        assert_eq!(unsafe { libc::KERNEL_VERSION(6, 0, 256) }, 393471);
+        assert_eq!(unsafe { libc::KERNEL_VERSION(6, 0, 300) }, 393471);
+        assert_eq!(unsafe { libc::KERNEL_VERSION(6, 0, u32::MAX) }, 393471);
     }
 }

src/unix/linux_like/mod.rs

@@ -1756,11 +1756,7 @@ safe_f! {
 
     #[allow(ellipsis_inclusive_range_patterns)]
     pub {const} fn KERNEL_VERSION(a: u32, b: u32, c: u32) -> u32 {
-        ((a << 16) + (b << 8))
-            + match c {
-                0..=255 => c,
-                _ => 255,
-            }
+        ((a << 16) + (b << 8)) + if c > 255 { 255 } else { c }
     }
 }