x86/vector: Fix the args of vector_alloc tracepoint

The vector_alloc tracepont reversed the reserved and ret aggs, that made
the trace print wrong. Exchange them.

Fixes: 8d1e3dca ("x86/vector: Add tracepoints for vector management")
Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: hpa@zytor.com
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20180601065031.21872-1-douly.fnst@cn.fujitsu.com