clk: zynqmp: Add a check for NULL pointer

[ Upstream commit 6ab9810c ]

Add a NULL pointer check as clk_hw_get_parent can return NULL.

Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Link: https://lore.kernel.org/r/20220518055314.2486-1-shubhrajyoti.datta@xilinx.com


Acked-by: Michal Simek <michal.simek@amd.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Stable-dep-of: 1fe15be1 ("drivers: clk: zynqmp: update divider round rate logic")
Signed-off-by: Sasha Levin <sashal@kernel.org>