[nrf noup] Remove setting default MCUboot mbedTLS config

This has been overriding logic that selects nrf-config.h
when CONFIG_NRF_SECURITY=y.

Signed-off-by: Dominik Ermel <[email protected]>
(cherry picked from commit ea00c04)
(cherry picked from commit 62929e4)

Author: de-nordic

boot/zephyr/prj.conf

@@ -1,7 +1,6 @@
 CONFIG_PM=n
 
 CONFIG_MAIN_STACK_SIZE=10240
-CONFIG_MBEDTLS_CFG_FILE="mcuboot-mbedtls-cfg.h"
 
 CONFIG_BOOT_SWAP_SAVE_ENCTLV=n
 CONFIG_BOOT_ENCRYPT_IMAGE=n