MIPS: TXx9: Microoptimize interrupt handlers

The IOC interrupt status register on RBTX49XX only have 8 bits.  Use
8-bit version of __fls() to optimize interrupt handlers.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/txx9/rbtx4927/irq.c b/arch/mips/txx9/rbtx4927/irq.c
index 22076e3..9c14ebb 100644
--- a/arch/mips/txx9/rbtx4927/irq.c
+++ b/arch/mips/txx9/rbtx4927/irq.c
@@ -133,9 +133,9 @@
 	u8 level3;
 
 	level3 = readb(rbtx4927_imstat_addr) & 0x1f;
-	if (level3)
-		sw_irq = RBTX4927_IRQ_IOC + fls(level3) - 1;
-	return sw_irq;
+	if (unlikely(!level3))
+		return -1;
+	return RBTX4927_IRQ_IOC + __fls8(level3);
 }
 
 static void __init toshiba_rbtx4927_irq_ioc_init(void)
diff --git a/arch/mips/txx9/rbtx4938/irq.c b/arch/mips/txx9/rbtx4938/irq.c
index ca2f830..7d21bef 100644
--- a/arch/mips/txx9/rbtx4938/irq.c
+++ b/arch/mips/txx9/rbtx4938/irq.c
@@ -85,10 +85,10 @@
 	u8 level3;
 
 	level3 = readb(rbtx4938_imstat_addr);
-	if (level3)
-		/* must use fls so onboard ATA has priority */
-		sw_irq = RBTX4938_IRQ_IOC + fls(level3) - 1;
-	return sw_irq;
+	if (unlikely(!level3))
+		return -1;
+	/* must use fls so onboard ATA has priority */
+	return RBTX4938_IRQ_IOC + __fls8(level3);
 }
 
 static void __init