fix(mbedtls): fix mbedtls coverity issues

commit (a8eadc51 refactor(mbedtls): avoid including
MBEDTLS_CONFIG_FILE) avoids using config file directly and relies on
config file usage from mbedtls version.h

But we could build trusted boot without mbedtls dir so guard version.h
include in cot_def.h with availability of config file.

Also we refactored in same commit to break dependencies between
auth_mod.h and cot_def.h, So add cot_def.h include in nxp tbbr
cot file.

Change-Id: I4779e90c18f04c73d2121c88df6420b4b1109c8b
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>