[PATCH] wireless-regdb: update regulatory rules for Bangladesh (BD) to allow 6 GHz (UNII-5)

[blackbird]

Dear Maintainers,


The Bangladesh Telecommunication Regulatory Commission (BTRC) has officially approved the lower portion of the 6 GHz frequency band (5925–6425 MHz) for shared, unlicensed use including Wi-Fi 6E/7, IoT, and Wireless LAN (WLAN) devices. 


Please update the database rules for Bangladesh (BD) to permit indoor transmissions on the UNII-5 band up to a 160 MHz channel width.


Official Regulatory References and Direct Circular Evidence:
- Official Announcement Notice Page: 
https://btrc.gov.bd/pages/notices/6922ee00dbfbab28ce0c438d
- Direct Source Regulatory PDF Document: 
https://objectstorage.ap-dcc-gazipur-1.oraclecloud15.com/n/axvjbnqprylg/b/V2Ministry/o/office-btrc/2024/12/18337854ab6c487fa749464c7672c8a8.pdf


Proposed database block update for db.txt:


country BD: DFS-FCC
(2402 - 2482 @ 40), (20)
(5170 - 5250 @ 80), (23)
(5735 - 5835 @ 80), (30)
# 6 GHz band (UNII-5) approved by BTRC circular on Sept 15, 2024
# Shared unlicensed indoor use for Wi-Fi, IoT, and WLAN
(5925 - 6425 @ 160), (23), NO-OUTDOOR


Signed-off-by: Syed Mubashir <jewel_boss_m at yahoo.com>