clk/zynq: Fix possible memory leak

The zynq_clk_register_fclk function can leak memory (fclk_lock) when unable
to alloc memory for fclk_gate_lock

Signed-off-by: Felipe Pena <felipensp@gmail.com>
Acked-by: Sören Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>