fix(st-clock): use Boolean type for tests

This corrects MISRA C2012-14.4
The controlling expression of an if statement and the controlling
expression of an iteration-statement shall have essentially Boolean type.

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: Id217d3da223caf75cd0439d7ce11c9efab87b4d2
2 files changed