clk: zynqmp: Off by one in zynqmp_is_valid_clock()

The > comparison should be >= to prevent reading beyond the end of the
clock[] array.

(The clock[] array is allocated in zynqmp_clk_setup() and has
clock_max_idx elements.)

Fixes: 3fde0e16 ("drivers: clk: Add ZynqMP clock driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>