mesa: Rename GLX_USE_TLS to USE_ELF_TLS.

These days it is not GLX only and it does not work with all TLS
implementations.

Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>
diff --git a/meson.build b/meson.build
index 2ca672e..61fc864 100644
--- a/meson.build
+++ b/meson.build
@@ -375,9 +375,9 @@
   endif
 endif
 
-# Android uses emutls for versions <= P/28. For GLX_USE_TLS we need ELF TLS.
+# Android uses emutls for versions <= P/28. For USE_ELF_TLS we need ELF TLS.
 if not with_platform_android or get_option('platform-sdk-version') >= 29
-  pre_args += '-DGLX_USE_TLS'
+  pre_args += '-DUSE_ELF_TLS'
 endif
 
 if with_glx != 'disabled'