Add iopl/ioperm to musl x86_64

Note that I think this is available on more than x86_64, but that is
all that I have to test. This also matches what was done for glibc
systems.

(backport <rust-lang#3720>)
(cherry picked from commit 083499a)

libc-test/semver/linux-i686.txt

@@ -214,6 +214,8 @@ fsblkcnt64_t
 fsfilcnt64_t
 getcontext
 greg_t
+ioperm
+iopl
 makecontext
 max_align_t
 mcontext_t

libc-test/semver/linux-x86_64.txt

@@ -139,6 +139,8 @@ TIOCGRS485
 TIOCSBRK
 TIOCSRS485
 greg_t
+ioperm
+iopl
 max_align_t
 mcontext_t
 ucontext_t

src/unix/linux_like/linux/gnu/b64/x86_64/mod.rs

@@ -802,8 +802,6 @@ extern "C" {
     pub fn setcontext(ucp: *const ucontext_t) -> ::c_int;
     pub fn makecontext(ucp: *mut ucontext_t, func: extern "C" fn(), argc: ::c_int, ...);
     pub fn swapcontext(uocp: *mut ucontext_t, ucp: *const ucontext_t) -> ::c_int;
-    pub fn iopl(level: ::c_int) -> ::c_int;
-    pub fn ioperm(from: ::c_ulong, num: ::c_ulong, turn_on: ::c_int) -> ::c_int;
 }
 
 cfg_if! {

src/unix/linux_like/linux/mod.rs

@@ -1556,6 +1556,16 @@ cfg_if! {
     }
 }
 
+cfg_if! {
+    if #[cfg(all(any(target_env = "gnu", target_env = "musl", target_env = "ohos"),
+                 any(target_arch = "x86_64", target_arch = "x86")))] {
+        extern "C" {
+            pub fn iopl(level: ::c_int) -> ::c_int;
+            pub fn ioperm(from: ::c_ulong, num: ::c_ulong, turn_on: ::c_int) -> ::c_int;
+        }
+    }
+}
+
 cfg_if! {
     if #[cfg(any(target_env = "gnu", target_env = "musl", target_env = "ohos"))] {
         pub const ABDAY_1: ::nl_item = 0x20000;