Revert "nir: make tgsi_varying_semantic_to_slot(..) public"

This reverts commit edbdd97723.

As etnaviv's TGSI compiler is gone we make that function
private again.

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Acked-by: Lucas Stach <l.stach@pengutronix.de>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12889>

src/gallium/auxiliary/nir/tgsi_to_nir.c

@@ -100,7 +100,7 @@ struct ttn_compile {
 #define ttn_channel(b, src, swiz) \
    nir_channel(b, src, TGSI_SWIZZLE_##swiz)
 
-gl_varying_slot
+static gl_varying_slot
 tgsi_varying_semantic_to_slot(unsigned semantic, unsigned index)
 {
    switch (semantic) {

src/gallium/auxiliary/nir/tgsi_to_nir.h

@@ -40,9 +40,6 @@ struct nir_shader *
 tgsi_to_nir_noscreen(const void *tgsi_tokens,
                      const nir_shader_compiler_options *options);
 
-gl_varying_slot
-tgsi_varying_semantic_to_slot(unsigned semantic, unsigned index);
-
 #ifdef __cplusplus
 }
 #endif