etmem scan: fix memleak in vm_idle_read

euleros inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I7RO5Q
CVE: NA
Reference: https://gitee.com/openeuler/kernel/commit/16af7936ee7836d37c39457250479845a1c1f842



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free pic before return from vm_idle_read in etmem scan

Signed-off-by: Kemeng Shi <shikemeng@huawei.com>
Reviewed-by: louhongxiang <louhongxiang@huawei.com>
Reviewed-by: Chen Wandun <chenwandun@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>