staging: rtl8723bs: remove GetHexValueFromString

Remove function GetHexValueFromString because it is not used.

Signed-off-by: Nam Cao <namcaov@gmail.com>
Link: https://lore.kernel.org/r/74c77a5d86570065a5fe96446063595b649f76b0.1662111798.git.namcaov@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>