nvme-pci: expose use_threaded_interrupts read-only in sysfs

Allow reading /sys/module/nvme/parameters/use_threaded_interrupts to see
if the use_threaded_interrupts module parameter is in use.
Signed-off-by: NXin Hao <xhao@linux.alibaba.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>

drivers/nvme/host/pci.c

@@ -44,7 +44,7 @@
 #define NVME_MAX_SEGS	127
 
 static int use_threaded_interrupts;
-module_param(use_threaded_interrupts, int, 0);
+module_param(use_threaded_interrupts, int, 0444);
 
 static bool use_cmb_sqes = true;
 module_param(use_cmb_sqes, bool, 0444);