clk: gate: expose clk_gate_ops::is_enabled

This patch exposes clk_gate_ops::is_enabled as functions
that can be directly called and assigned in places like this so
we don't need wrapper functions that do nothing besides forward
the call.

Signed-off-by: Gabriel Fernandez <gabriel.fernandez@st.com>
Suggested-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>