gallium/docs: Fix an inequality sign of TGSI_SEMANTIC_SUBGROUP_LT_MASK

A previous expression presents same as TGSI_SEMANTIC_SUBGROUP_GT_MASK.
It fixes a direction of an inequality for TGSI_SEMANTIC_SUBGROUP_LT_MASK.

before:
  bit index > TGSI_SEMANTIC_SUBGROUP_INVOCATION

after:
  bit index < TGSI_SEMANTIC_SUBGROUP_INVOCATION

Signed-off-by: Mun Gwan-gyeong <elongbug@gmail.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
diff --git a/src/gallium/docs/source/tgsi.rst b/src/gallium/docs/source/tgsi.rst
index 31331ef..0bd9964 100644
--- a/src/gallium/docs/source/tgsi.rst
+++ b/src/gallium/docs/source/tgsi.rst
@@ -3397,7 +3397,7 @@
 TGSI_SEMANTIC_SUBGROUP_LT_MASK
 """"""""""""""""""""""""""""""
 
-A bit mask of ``bit index > TGSI_SEMANTIC_SUBGROUP_INVOCATION``, i.e.
+A bit mask of ``bit index < TGSI_SEMANTIC_SUBGROUP_INVOCATION``, i.e.
 ``(1 << subgroup_invocation) - 1`` in arbitrary precision arithmetic.