rust: io: mem: enable IoRequest doc-tests

When introduced, the IoRequest doc-tests did depend on infrastructure
added in subsequent patches, hence they temporarily had to be disabled.

Now that we have the corresponding platform device infrastructure,
enable them.

Link: https://lore.kernel.org/r/DBG39YMN2TX6.1VR4PEQSI8PSG@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Author: Danilo Krummrich

rust/kernel/io/mem.rs

@@ -43,7 +43,7 @@ impl<'a> IoRequest<'a> {
     /// The following example uses a [`platform::Device`] for illustration
     /// purposes.
     ///
-    /// ```ignore
+    /// ```no_run
     /// use kernel::{bindings, c_str, platform, of, device::Core};
     /// struct SampleDriver;
     ///
@@ -101,7 +101,7 @@ impl<'a> IoRequest<'a> {
     /// The following example uses a [`platform::Device`] for illustration
     /// purposes.
     ///
-    /// ```ignore
+    /// ```no_run
     /// use kernel::{bindings, c_str, platform, of, device::Core};
     /// struct SampleDriver;
     ///