clk: keystone: sci-clk: check return value of kasprintf()

clk: keystone: sci-clk: 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: b745c0794e2f ("clk: keystone: Add sci-clk driver support")
Depends-on: 96488c09b0f4 ("clk: keystone: sci-clk: cut down the clock name length")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20230530093913.1656095-7-claudiu.beznea@microchip.com
Reviewed-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>