llvmpipe: increase max texture size to 2GB

The 1GB limit was arbitrary, increase this to 2GB (which is the max
possible without code changes).

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>

src/gallium/drivers/llvmpipe/lp_limits.h

@@ -43,7 +43,11 @@
 /**
  * Max texture sizes
  */
-#define LP_MAX_TEXTURE_SIZE (1 * 1024 * 1024 * 1024ULL)  /* 1GB for now */
+/**
+ * 2GB is the actual max currently (we always use 32bit offsets, and both
+ * llvm GEP as well as avx2 gather use signed offsets).
+ */
+#define LP_MAX_TEXTURE_SIZE (2 * 1024 * 1024 * 1024ULL)
 #define LP_MAX_TEXTURE_2D_LEVELS 14  /* 8K x 8K for now */
 #define LP_MAX_TEXTURE_3D_LEVELS 12  /* 2K x 2K x 2K for now */
 #define LP_MAX_TEXTURE_CUBE_LEVELS 14  /* 8K x 8K for now */