sched/irq: Fix nxstyle declaration spacing.

Add the required blank line between the intcount declaration and the
following statement.

Assisted-by: OpenAI Codex
Signed-off-by: yushuailong <yyyusl@qq.com>

sched/irq/irq_procfs.c

@@ -214,6 +214,7 @@ static int irq_callback(int irq, FAR struct irq_info_s *info,
   else
     {
       uint64_t intcount = ((uint64_t)intpart * elapsed);
+
       fracpart = (unsigned int)
         (((copy.count * TICK_PER_SEC - intcount) * 1000) / elapsed);
     }