wifi: mt76: mt7921: Check devm_kasprintf() returned value

commit 1ccc9e47 upstream.

devm_kasprintf() can return a NULL pointer on failure but this returned
value is not checked. Fix this lack and check the returned value.

Found by code review.

Cc: stable@vger.kernel.org
Fixes: 6ae39b7c ("wifi: mt76: mt7921: Support temp sensor")
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
Reviwed-by: Matthias Brugger <matthias.bgg@gmail.com>
Link: https://patch.msgid.link/20240903014455.4144536-1-make24@iscas.ac.cn


Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>