clk: Fix typo in comment

CLK_MUX_INDEX_BIT is mistakenly written as CLK_MUX_INDEX_BITWISE in comment. Fix
it.

CLK_GATE_SET_TO_DISABLE is mistakenly written as CLK_GATE_SET_DISABLE in
comment. Fix it.

Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>