fs/ntfs3: Use linux/log2 is_power_of_2 function

We do not need our own implementation for this function in this
driver. It is much better to use generic one.

Signed-off-by: Kari Argillander <kari.argillander@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>