MLK-20204: drivers: crypto: caam: sm: Remove deadcode

MLK-20204: drivers: crypto: caam: sm: Remove deadcode

There was some code to free the keystore but the current
state of the function make this code unreachable so
remove it.

Coverity explanation:
drivers/crypto/caam/sm_store.c:654: CID 17839 (#1 of 1):
  Type: Logically dead code (DEADCODE)
  Classification: Bug
  Severity: Major
  Action: Fix Required
  Owner: nxa21133
  Defect only exists locally.
drivers/crypto/caam/sm_store.c:625:
  cond_null: Condition "keystore_data == NULL", taking true branch. Now
  the value of "keystore_data" is "NULL".
drivers/crypto/caam/sm_store.c:653:
  null: At condition "keystore_data != NULL", the value of "keystore_data"
  must be "NULL".
drivers/crypto/caam/sm_store.c:653:
  dead_error_condition: The condition "keystore_data != NULL" cannot be
  true.
drivers/crypto/caam/sm_store.c:654:
  dead_error_line: Execution cannot reach this statement:
  "kfree(keystore_data);".

Signed-off-by: Franck LENORMAND <franck.lenormand@nxp.com>