pm: cpupower: bench: Prevent NULL dereference on malloc failure

[ Upstream commit 208baa3ec9043a664d9acfb8174b332e6b17fb69 ]

If malloc returns NULL due to low memory, 'config' pointer can be NULL.
Add a check to prevent NULL dereference.

Link: https://lore.kernel.org/r/20250219122715.3892223-1-quic_zhonhan@quicinc.com


Signed-off-by: Zhongqiu Han <quic_zhonhan@quicinc.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>