wio.cgi: Fixes bug#13039 - Input boxes extend outside of WUI boundary with some browsers

wio.cgi: Fixes bug#13039 - Input boxes extend outside of WUI boundary with some browsers

- Original poster found this effect with using Vivaldi at 100% zoom.
- I tested it with Vivaldi and Firefox on Arch Linux and was not able to show the effect but
   running SeaMonkey and changing the zoom from 100% to lower or higher caused the input
   boxes to go outside of the WUI boundary as described by the bug reporter.
- It looks like the effect is dependent on the browser, the zoom setting and the OS
   Distribution.
- In all cases the similar three input boxes in a row in the dhcp.cgi code for entering a
   fixed lease stayed fixed in ratrio to the WUI page whatever zoom or browser was used.
- This patch changes the wio code for those three input boxes to use the approach from the
   dhcp.cgi code.
- Tested on my vm testbed and change confirmed to fix the size of the input boxes
   irrespective of the browser or zoom setting.

Fixes: Bug#13039
Tested-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>