wifi: rtw89: add debugfs entry of monitor mode options to capture HE-MU packets

wifi: rtw89: add debugfs entry of monitor mode options to capture HE-MU packets

To capture HE-MU packets, set BSS color and AID for specific connected
station.

The writing format: <bss color> <aid>
For example,
  $ echo 0x4 0x16 > monitor_opts

Read this entry to get current setting:
  bss_color=0x4 aid=0x16

By the way, add another sec2() function to create debugfs entries to
prevent running smatch timeout.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20260506131000.1706298-11-pkshih@realtek.com