clk/zynq/clkc: Add dedicated spinlock for the SWDT

The clk_mux for the system watchdog timer reused the register lock
dedicated to the Ethernet module - for no apparent reason.
Add a lock dedicated to the SWDT's clock register to remove this
wrong dependency.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
clk/zynq/clkc: Add CLK_SET_RATE_PARENT flag to ethernet muxes

Zynq's Ethernet clocks are created by the following hierarchy:
	mux0 ---> div0 ---> div1 ---> mux1 ---> gate
Rate change requests on the gate have to propagate all the way up to
div0 to properly leverage all dividers. Mux1 was missing the
CLK_SET_RATE_PARENT flag, which is required to achieve this.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>