wifi: rtw89: debugfs: implement file_ops::read/write to replace seq_file

Since debugfs needs wiphy lock held, wiphy_locked_debugfs_{read,write}()
will be adopted, so implmenet file_ops::read/write along with their
arguments.

For reading part, it needs lots of changes because seq_file is not
suitable for wiphy_locked_debugfs_{read,write}(), so use spatch script
below to convert basically, and manually implement the functions.

  @ rule1 @
  identifier m;
  @@

  - seq_printf(m,
  + p += scnprintf(p, end - p,
    ...)

  @ rule2 @
  identifier m;
  @@

  - seq_puts(m,
  + p += scnprintf(p, end - p,
    ...)

For current version, only 4K buffer to output. To note ourselves, add
ellipsis symbol "..." to trailing if buffer is full. Later, add an option
to specify buffer size needed by a debugfs entry.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20250122060310.31976-4-pkshih@realtek.com