staging: r8188eu: remove HW_VAR_BCN_FUNC

staging: r8188eu: remove HW_VAR_BCN_FUNC

The HW_VAR_BCN_FUNC case in SetHwReg8188EU() just calls
hw_var_set_bcn_func(). Remove HW_VAR_BCN_FUNC from SetHwReg8188EU(),
remove hw_var_set_bcn_func() and call rtw_write8() directly.

Since hw_var_set_bcn_func() was always called with value 0, we only
need to keep the else arm of the if statement that checks the value.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20220130190321.7172-11-straube.linux@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>