Remove NULL pointer validation in pk.c
Remove NULL pointer validation in pk.c

Signed-off-by: Tuvshinzaya Erdenekhuu <995488366c88e45a5bab05b84d5ad695ef4d0a71@arm.com>

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