staging: speakup: Remove multiple assignments

Remove multiple assignments by factorizing them.Problem found using
checkpatch.pl
CHECK: multiple assignments should be avoided
Signed-off-by: Burcin Akalin <brcnakalin@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/speakup/buffers.c

@@ -101,6 +101,7 @@ EXPORT_SYMBOL_GPL(synth_buffer_peek);
 
 void synth_buffer_clear(void)
 {
-	buff_in = buff_out = synth_buffer;
+	buff_in = synth_buffer;
+	buff_out = synth_buffer;
 }
 EXPORT_SYMBOL_GPL(synth_buffer_clear);