core: MIPS: Disable four f16 doctests that fails to link

Otherwise they fail to link with

    undefined reference to `__gnu_h2f_ieee'
    undefined reference to `__gnu_f2h_ieee'

Author: Martin Nordholts

library/core/src/num/f16.rs

@@ -509,12 +509,15 @@ impl f16 {
     /// #![feature(f16)]
     /// # // FIXME(f16_f128): remove when `extendhfsf2` and `truncsfhf2` are available
     /// # #[cfg(target_os = "linux")] {
+    /// # // FIXME(f16_f128): remove when `__gnu_h2f_ieee` and `__gnu_f2h_ieee` are available
+    /// # #[cfg(not(all(target_arch = "mips", target_os = "linux")))] {
     ///
     /// let x = 2.0_f16;
     /// let abs_difference = (x.recip() - (1.0 / x)).abs();
     ///
     /// assert!(abs_difference <= f16::EPSILON);
     /// # }
+    /// # }
     /// ```
     #[inline]
     #[cfg(not(bootstrap))]
@@ -530,12 +533,15 @@ impl f16 {
     /// #![feature(f16)]
     /// # // FIXME(f16_f128): remove when `extendhfsf2` and `truncsfhf2` are available
     /// # #[cfg(target_os = "linux")] {
+    /// # // FIXME(f16_f128): remove when `__gnu_h2f_ieee` and `__gnu_f2h_ieee` are available
+    /// # #[cfg(not(all(target_arch = "mips", target_os = "linux")))] {
     ///
     /// let angle = std::f16::consts::PI;
     ///
     /// let abs_difference = (angle.to_degrees() - 180.0).abs();
     /// assert!(abs_difference <= 0.5);
     /// # }
+    /// # }
     /// ```
     #[inline]
     #[cfg(not(bootstrap))]
@@ -553,13 +559,16 @@ impl f16 {
     /// #![feature(f16)]
     /// # // FIXME(f16_f128): remove when `extendhfsf2` and `truncsfhf2` are available
     /// # #[cfg(target_os = "linux")] {
+    /// # // FIXME(f16_f128): remove when `__gnu_h2f_ieee` and `__gnu_f2h_ieee` are available
+    /// # #[cfg(not(all(target_arch = "mips", target_os = "linux")))] {
     ///
     /// let angle = 180.0f16;
     ///
     /// let abs_difference = (angle.to_radians() - std::f16::consts::PI).abs();
     ///
     /// assert!(abs_difference <= 0.01);
     /// # }
+    /// # }
     /// ```
     #[inline]
     #[cfg(not(bootstrap))]
@@ -870,6 +879,8 @@ impl f16 {
     ///
     /// ```
     /// #![feature(f16)]
+    /// # // FIXME(f16_f128): remove when `__gnu_h2f_ieee` and `__gnu_f2h_ieee` are available
+    /// # #[cfg(not(all(target_arch = "mips", target_os = "linux")))] {
     ///
     /// struct GoodBoy {
     ///     name: &'static str,
@@ -897,6 +908,7 @@ impl f16 {
     ///         .zip([-5.0, 0.1, 10.0, 99.0, f16::INFINITY, f16::NAN].iter())
     ///         .for_each(|(a, b)| assert_eq!(a.to_bits(), b.to_bits()))
     /// }
+    /// # }
     /// ```
     #[inline]
     #[must_use]