MCUboot: configuration file ignored

[JordanYates]

Describe the bug

When building an application with MCUboot support, the configuration file specified by MCUboot is overridden, resulting in build system warnings.

To Reproduce

west build -b nrf52840dk/nrf52840 samples/hello_world/ --sysbuild -p -- -DSB_CONFIG_BOOTLOADER_MCUBOOT=y
...
warning: MBEDTLS_CFG_FILE (defined at
/home/jordan/code/zephyr/bootloader/mcuboot/boot/zephyr/Kconfig:288, modules/mbedtls/Kconfig:52,
modules/mbedtls/Kconfig:52) was assigned the value 'mcuboot-mbedtls-cfg.h' but got the value
'config-tls-generic.h'. See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_MBEDTLS_CFG_FILE and/or look up
MBEDTLS_CFG_FILE in the menuconfig/guiconfig interface. The Application Development Primer, Setting
Configuration Values, and Kconfig - Tips and Best Practices sections of the manual might be helpful
too.
...

Expected behavior

No build system warnings when building a default MCUboot application

Environment (please complete the following information):

• Zephyr v4.1.0-rc2