nvme-cli: error-log: Fix memory leak for JSON.

nvme-cli: error-log: Fix memory leak for JSON.

This patch fixes the following memory leak when error-log command
executed with JSON option:-
==7690==
==7690== HEAP SUMMARY:
==7690==     in use at exit: 49,779 bytes in 1,708 blocks
==7690==   total heap usage: 2,242 allocs, 534 frees, 87,392 bytes allocated
==7690==
==7690== LEAK SUMMARY:
==7690==    definitely lost: 24 bytes in 1 blocks
==7690==    indirectly lost: 49,755 bytes in 1,707 blocks
==7690==      possibly lost: 0 bytes in 0 blocks
==7690==    still reachable: 0 bytes in 0 blocks
==7690==         suppressed: 0 bytes in 0 blocks

Fix:-
==8015==
==8015== HEAP SUMMARY:
==8015==     in use at exit: 0 bytes in 0 blocks
==8015==   total heap usage: 2,242 allocs, 2,242 frees, 87,392 bytes allocated
==8015==

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@hgst.com>