[BUG] `stat()` does not work on flash partition with BCH layer

### Description / Steps to reproduce the issue

Flash partition configured as BCH layer (device driver created with `bchdev_register`) doesn't allow `stat` call to obtain the information about an underlying MTD device/flash. This is caused by `INODE_IS_MTD` not being set and thus
function `inode_stat` falls to the last `else` statement and does not fill the necessary information.

This is a logical output as BCH layer is registered as a standard character device driver, therefore it is not considered as MTD but as a standard driver (ADC, PWM, etc.). This, however, makes the `stat` call unusable for it.

We should probably find a way how to pass an information there is a MTD device under the driver and that we should access it with a standard `MTDIOC_GEOMETRY` ioctl to obtain the required information and pass them to the user.

### On which OS does this issue occur?

[OS: Linux]

### What is the version of your OS?

Ubuntu 22.04.5 LTS

### NuttX Version

master

### Issue Architecture

[Arch: all]

### Issue Area

[Area: Kernel], [Area: Drivers]

### Host information

_No response_

### Verification

- [x] I have verified before submitting the report.