luci-app-dawn: Fix getChannelFromFrequency for 6GHz

[PIPIPIG233666]

• This PR is not from my main or master branch 💩, but a separate branch ✅
• Each commit has a valid ✒️ Signed-off-by: <my@email.address> row (via git commit --signoff)
• Each commit and PR title has a valid 📝 <package name>: title first line subject for packages
• Incremented 🆙 any PKG_VERSION in the Makefile
• Tested on: (qualcommax, main, MS edge) ✅
  - [ ] ( Preferred ) Mention: @ the original code author for feedback
• ( Preferred ) Screenshot or mp4 of changes:
  

- [ ] ( Optional ) Closes: e.g. openwrt/luci#issue-number
- [ ] ( Optional ) Depends on: e.g. openwrt/packages#pr-number in sister repo

• Description: (describe the changes proposed in this PR)
  The calculation is as follows:
  (6GHz freq - 5950) / 5

i.e. (6135 - 5950) / 5 = 185 / 5 = 33

[systemcrash]

Reformat your commit message to at least be mathematically correct.

The calculation is as follows:
(6GHz freq - 5950) / 5

i.e. (6135 - 5950) / 5 = 185 / 5 = 33

(6135 - 5950) / 5 ≠ 185

6135 - 5950 = 185

185 / 5 = 37

Revise to:

For (5.9-)6GHz channels
Center Frequency = 5950 + ( 5 * channel_number )
or
( Center Frequency - 5950 ) / 5 = channel_number

e.g. 
( 1 * 5  ) + 5950 = 5955MHz
or
( 5955 - 5950 ) / 5 = Channel 1

[PIPIPIG233666]

Reformat your commit message to at least be mathematically correct.

The calculation is as follows:
(6GHz freq - 5950) / 5

i.e. (6135 - 5950) / 5 = 185 / 5 = 33

(6135 - 5950) / 5 ≠ 185

6135 - 5950 = 185

185 / 5 = 37

Revise to:

For (5.9-)6GHz channels
Center Frequency = 5950 + ( 5 * channel_number )
or
( Center Frequency - 5950 ) / 5 = channel_number

e.g. 
( 1 * 5  ) + 5950 = 5955MHz
or
( 5955 - 5950 ) / 5 = Channel 1

Okay 33 was a typo in the message, meant to type 37. The change itself is correct though.

(6135 - 5950) / 5 ≠ 185

Also I meant (6135-5950) first to get 185 how is this not mathematically correct...

[PIPIPIG233666]

Done

[systemcrash]

Merged. Thanks @PIPIPIG233666