freedreno/registers: Re-enable validation for gen_header.py

Commit 84e93daa26 ("freedreno/registers: allow skipping the
validation") synced a change that made validation optional for
kernel builds, to avoid a lxml dependency for kernel builds.
But this inadvertantly also disabled schema validation on the
mesa side.  CI (and meson "test" target) still validates the
xml against the schema, but it is easier if this is also done
as part of the normal build to avoid suprises from Marge.

Fixes: 84e93daa26 ("freedreno/registers: allow skipping the validation")
Signed-off-by: Rob Clark <rob.clark@oss.qualcomm.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37216>
(cherry picked from commit a70279adc2)

.pick_status.json

@@ -7474,7 +7474,7 @@
         "description": "freedreno/registers: Re-enable validation for gen_header.py",
         "nominated": true,
         "nomination_type": 2,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "84e93daa265687ee6a54506c197e99793e7d3b2f",
         "notes": null

src/freedreno/registers/adreno/meson.build

@@ -32,7 +32,7 @@ foreach f : xml_files
     _name,
     input: [gen_header_py, f, freedreno_schema, freedreno_copyright],
     output: _name,
-    command: [prog_python, '@INPUT0@', '--rnn', rnn_src_path, '--xml', '@INPUT1@', 'c-defines'],
+    command: [prog_python, '@INPUT0@', '--validate', '--rnn', rnn_src_path, '--xml', '@INPUT1@', 'c-defines'],
     capture: true,
   )
   _gzname = f + '.gz'

src/freedreno/registers/meson.build

@@ -22,7 +22,7 @@ foreach f : xml_files
     _name,
     input: [gen_header_py, f, freedreno_schema, freedreno_copyright],
     output: _name,
-    command: [prog_python, '@INPUT0@', '--rnn', rnn_src_path, '--xml', '@INPUT1@', 'c-defines'],
+    command: [prog_python, '@INPUT0@', '--validate', '--rnn', rnn_src_path, '--xml', '@INPUT1@', 'c-defines'],
     capture: true,
   )
 endforeach