scripts: kconfig: Always generate ZEPHYR_*_MODULE

Define the ZEPHYR_{MODULE_NAM}_MODULE option for all available modules.
Right now only modules defined as 'kconfig-ext' has this symbol defined
which may cause problem if the build wants to check if a module not
using this options is available.

This allow us to do something like:

comment "mbedTLS module not available."
	depends on !ZEPHYR_MBEDTLS_MODULE

or make a feature depends on the module be present.

Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>

scripts/zephyr_module.py

@@ -350,7 +350,10 @@ def process_kconfig(module, meta):
         return kconfig_snippet(meta, module_path, Path(kconfig_file),
                                blobs=taint_blobs)
     else:
-        return ""
+        name_sanitized = meta['name-sanitized']
+        return (f'config ZEPHYR_{name_sanitized.upper()}_MODULE\n'
+                f'   bool\n'
+                f'   default y\n')
 
 
 def process_sysbuildkconfig(module, meta):