Revert "ANDROID: ashmem: use strncpy_from_user in set_name"

This reverts commit ba971cd36a.

Bug: 414339114
Change-Id: If44d5a7516c7dfdda68272f629ce30d74c84694f
Signed-off-by: Alice Ryhl <aliceryhl@google.com>

rust/kernel/uaccess.rs

@@ -294,19 +294,6 @@ impl UserSliceReader {
         unsafe { buf.inc_len(len) };
         Ok(())
     }
-
-    /// Reads a nul-terminated string into the provided buffer and returns the length.
-    pub fn strncpy_from_user(self, buf: &mut [u8]) -> Result<usize> {
-        let max = usize::min(self.length, buf.len()) as isize;
-        // SAFETY: `buf` is valid for writing `buf.len()` bytes.
-        let res =
-            unsafe { bindings::strncpy_from_user(buf.as_mut_ptr(), self.ptr as *const u8, max) };
-        if res >= 0 {
-            Ok(res as usize)
-        } else {
-            Err(Error::from_errno(res as i32))
-        }
-    }
 }
 
 /// A writer for [`UserSlice`].