staging: rtl8723bs: remove function GetFractionValueFromString

because this function is not used.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Nam Cao <namcaov@gmail.com>
Link: https://lore.kernel.org/r/e782bcd3ff8c33df8da7eb6b8e4bb00b1c270edc.1660916523.git.namcaov@gmail.com


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