fs_inode:Change the type of i_crefs to atomic_int

[crafcat7]

Summary

Benefit from PR#13044, we can change the the inode->i_crefs to atomic. That we can avoid problems:
Deadlocks caused by the server requesting reads from the client and the client requesting writes from the server when operating a file system with multiple cores (e.g. RPMSGFS).

The main changes are as follows:
1.Modified the i_crefs from int16_t to atomic_int
2.Modified the i_crefs add, delete, read, and initialize interfaces to atomic operations

The main change of this PR is to change the i_crefs count of inode to atomic type and use atomic operations to maintain i_crefs.

Impact

Impact on user: NO, This is a change within VFS and should be transparent to external developers.
Impact on build: YES, This may affect compilation because the members of the inode structure have changed. Different compilers/platforms have different support for atomic, so some warnings are skipped.
Impact on compatibility: This implementation aims to be backward compatible. No existing functionality is expected to be broken.

Testing

Build Host(s): Linux x86
Target(s): sim/nsh

Basic operations on the file system can work normally

[anchao]

Please check that all i_crefs are replaced correctly, eg:
https://github.com/apache/nuttx/blob/master/drivers/serial/pty.c#L335

[anchao]

Ditto, please make sure to go through the code carefully
https://github.com/apache/nuttx/blob/master/fs/vfs/fs_dir.c#L83

[crafcat7]

Please check that all i_crefs are replaced correctly, eg: https://github.com/apache/nuttx/blob/master/drivers/serial/pty.c#L335

Done

Ditto, please make sure to go through the code carefully https://github.com/apache/nuttx/blob/master/fs/vfs/fs_dir.c#L83

Done

[crafcat7]

I found that some platforms have the following warning when using different compilers

====================================================================================
Configuration/Tool: samd20-xplained/nsh,CONFIG_ARM_TOOLCHAIN_CLANG
2024-09-14 17:29:29
------------------------------------------------------------------------------------
  Cleaning...
  Configuring...
  Disabling CONFIG_ARM_TOOLCHAIN_GNU_EABI
  Enabling CONFIG_ARM_TOOLCHAIN_CLANG
  Building NuttX...
Error: inode/fs_inodeaddref.c:50:7: error: large atomic operation may incur significant performance penalty; the access size (4 bytes) exceeds the max lock-free size (0  bytes) [-Werror,-Watomic-alignment]
   50 |       atomic_fetch_add(&inode->i_crefs, 1);

In the current strategy, if the compiler itself does not support Atomic, Nuttx Base Atomic (low-performance version) will be used. So can we ignore it?