clk: bcm/kona: Silence sparse warnings

drivers/clk/bcm/clk-kona.c:1243:16: warning: odd constant _Bool cast (ffffffffffffffea becomes 1)

Reviewed-by: Alex Elder <elder@linaro.org>
Cc: Tim Kryger <tim.kryger@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>