refactor(arm): use MBEDTLS_CONFIG_FILE macro

Used MBEDTLS_CONFIG_FILE macro for including mbedTLS
configuration.

Signed-off-by: Manish V Badarkhe <manish.badarkhe@arm.com>
Change-Id: I374b59a31df3ab1e69481b2c37a6f7455a106b6e
2 files changed