clk: ti: clkctrl: check return value of kasprintf()

kasprintf() 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: 85204959 ("clk: ti: clkctrl: convert subclocks to use proper names also")
Fixes: 6c309052 ("clk: ti: clkctrl: Fix hidden dependency to node name")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20230530093913.1656095-8-claudiu.beznea@microchip.com


Reviewed-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>