virt: acrn: Use EPOLLIN instead of POLLIN

This fixes the following sparse warning:
"sparse warnings: (new ones prefixed by >>)"
>> drivers/virt/acrn/irqfd.c:163:13: sparse: sparse: restricted __poll_t
 degrades to integer

Fixes: dcf9625f ("virt: acrn: Use vfs_poll() instead of f_op->poll()")
Reported-by: Nkernel test robot <lkp@intel.com>
Acked-by: NShuo Liu <shuo.a.liu@intel.com>
Signed-off-by: NYejune Deng <yejune.deng@gmail.com>
Link: https://lore.kernel.org/r/20210310074901.7486-1-yejune.deng@gmail.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/virt/acrn/irqfd.c

@@ -160,7 +160,7 @@ static int acrn_irqfd_assign(struct acrn_vm *vm, struct acrn_irqfd *args)
 	/* Check the pending event in this stage */
 	events = vfs_poll(f.file, &irqfd->pt);
 
-	if (events & POLLIN)
+	if (events & EPOLLIN)
 		acrn_irqfd_inject(irqfd);
 
 	fdput(f);