Prevent resource leak
Prevent resource leak

If -f was used as an argument twice to the program, then it would leak
the file resource, due to overwriting it on the second pass

Signed-off-by: Paul Elliott <c95151bd40fac1aa138ed1651e2873f91d2e1899@arm.com>

Mbed-TLS/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls