nvme: PEL need to check gen number for verification of collected log

nvme: PEL need to check gen number for verification of collected log

+fix bug(unallocated pointer free)

If the Persistent Event Log is not read with a single Get Log Page command,
then host software should read the Generation Number field in the Persistent Event Log header after establishing a reporting context
but before reading the remainder of the log and then re-read the Generation Number field after it has read the entire log.
If the generation numbers do not match, then:
    • the reporting context may have been lost while reading the log;
    • the Persistent Event Log contents read may be invalid; and
    • host software should re-read the log.

Signed-off-by: Steven Seungcheol Lee <sc108.lee@samsung.com>