phy: tegra: xusb: check return value of devm_kzalloc()

devm_kzalloc() returns a pointer to dynamically allocated memory.
Pointer could be NULL in case allocation fails. Check pointer validity.
Identified with coccinelle (kmerr.cocci script).

Fixes: f67213ce ("phy: tegra: xusb: Add usb-role-switch support")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20230531073950.145339-1-claudiu.beznea@microchip.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>