rust: pci: use to_result() in enable_device_mem()

Simplify enable_device_mem() by using to_result() to handle the return
value of the corresponding FFI call.

Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Acked-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20250314160932.100165-2-dakr@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Danilo Krummrich

rust/kernel/pci.rs

@@ -382,12 +382,7 @@ impl Device {
     /// Enable memory resources for this device.
     pub fn enable_device_mem(&self) -> Result {
         // SAFETY: `self.as_raw` is guaranteed to be a pointer to a valid `struct pci_dev`.
-        let ret = unsafe { bindings::pci_enable_device_mem(self.as_raw()) };
-        if ret != 0 {
-            Err(Error::from_errno(ret))
-        } else {
-            Ok(())
-        }
+        to_result(unsafe { bindings::pci_enable_device_mem(self.as_raw()) })
     }
 
     /// Enable bus-mastering for this device.