freedreno/rnn: update schema for 'pos'

Ideally we'd like to express that *either* 'high' + 'low' OR 'pos' is
required, but it doesn't appear that this is possible.  But the rnn
parsing code should still enforce this.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6107>
diff --git a/src/freedreno/registers/rules-ng.xsd b/src/freedreno/registers/rules-ng.xsd
index 10b5f37..a5a3341 100644
--- a/src/freedreno/registers/rules-ng.xsd
+++ b/src/freedreno/registers/rules-ng.xsd
@@ -181,8 +181,9 @@
 			<group ref="rng:topGroup" />

 		</choice>

 		<attribute name="name" type="NMTOKEN" use="required" />

-		<attribute name="high" type="nonNegativeInteger" use="required" />

-		<attribute name="low" type="nonNegativeInteger" use="required" />

+		<attribute name="high" type="nonNegativeInteger" use="optional" />

+		<attribute name="low" type="nonNegativeInteger" use="optional" />

+		<attribute name="pos" type="nonNegativeInteger" use="optional" />

 		<attribute name="type" type="NMTOKENS" use="optional" />

 		<attribute name="varset" type="NMTOKEN" use="optional" />

 		<attribute name="variants" type="string" use="optional" />