staging: rtl8723bs: Remove function pointer set_tx_power_level_handler

Remove function pointer set_tx_power_level_handler as it is not in use.

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/e120c858d268eaae822ca0b582e453af06ef0891.1730749680.git.philipp.g.hortmann@gmail.com


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