clk: si5341: check return value of {devm_}kasprintf()

{devm_}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: 3044a860 ("clk: Add Si5341/Si5340 driver")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20230530093913.1656095-5-claudiu.beznea@microchip.com


Signed-off-by: Stephen Boyd <sboyd@kernel.org>