cpufreq/longhaul: handle NULL policy in longhaul_exit

cpufreq/longhaul: handle NULL policy in longhaul_exit

[ Upstream commit 592532a77b736b5153e0c2e4c74aa50af0a352ab ]

longhaul_exit() was calling cpufreq_cpu_get(0) without checking
for a NULL policy pointer. On some systems, this could lead to a
NULL dereference and a kernel warning or panic.

This patch adds a check using unlikely() and returns early if the
policy is NULL.

Bugzilla: #219962

Signed-off-by: Dennis Beier <nanovim@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>