atm: idt77252: remove unused function

Fix the following clang warning:

drivers/atm/idt77252.c:1787:1: warning: unused function
'idt77252_fbq_level' [-Wunused-function].
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/atm/idt77252.c

@@ -1783,12 +1783,6 @@ set_tct(struct idt77252_dev *card, struct vc_map *vc)
 /*                                                                           */
 /*****************************************************************************/
 
-static __inline__ int
-idt77252_fbq_level(struct idt77252_dev *card, int queue)
-{
-	return (readl(SAR_REG_STAT) >> (16 + (queue << 2))) & 0x0f;
-}
-
 static __inline__ int
 idt77252_fbq_full(struct idt77252_dev *card, int queue)
 {