[nrf noup] modules: mbedtls: Allow MBEDTLS_BUILTIN to be deselected

Out-of-tree crypto subsystems need to deselect MBEDTLS_BUILTIN, but
deselection is not supported. It is however supported to select a
dependency in a ! expression.

Signed-off-by: Sebastian Bøe <[email protected]>
(cherry picked from commit e261976)
(cherry picked from commit 906921d)

Author: SebastianBoe

modules/mbedtls/Kconfig

@@ -28,6 +28,7 @@ choice MBEDTLS_IMPLEMENTATION
 
 config MBEDTLS_BUILTIN
 	bool "Use Zephyr in-tree mbedTLS version"
+	depends on ! DISABLE_MBEDTLS_BUILTIN
 	help
 	  Link with mbedTLS sources included with Zephyr distribution.
 	  Included mbedTLS version is well integrated with and supported
@@ -41,6 +42,11 @@ config MBEDTLS_LIBRARY
 
 endchoice
 
+# subsystems cannot deselect MBEDTLS_BUILTIN, but they can select
+# DISABLE_MBEDTLS_BUILTIN.
+config DISABLE_MBEDTLS_BUILTIN
+	bool
+
 config CUSTOM_MBEDTLS_CFG_FILE
 	bool "Custom mbed TLS configuration file"
 	help