Fix missing parentheses.

The BIONIC_ROUND_UP_POWER_OF_2 macro did not have parentheses around
the whole expression. This lead to the wrong value being computed when
used as part of a mathematical expression such as this:

  value = BIONIC_ROUND_UP_POWER_OF_2(value) - 1;

This only happens on 64 bit abis.

Change-Id: I6f8afbdaf16fe64a88fa0246d074b3534c9159c1