Blackfin: bf537-stamp: change CONFIG_USB_SL811_BFIN_IRQ to IRQ_PF4

The Kconfig option was never mainlined, so replace the define with the
actual pin that it is hooked up to by default.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/arch/blackfin/mach-bf537/boards/stamp.c b/arch/blackfin/mach-bf537/boards/stamp.c
index 03e36bd..3402236 100644
--- a/arch/blackfin/mach-bf537/boards/stamp.c
+++ b/arch/blackfin/mach-bf537/boards/stamp.c
@@ -208,8 +208,8 @@
 		.end = 0x20340004,
 		.flags = IORESOURCE_MEM,
 	}, {
-		.start = CONFIG_USB_SL811_BFIN_IRQ,
-		.end = CONFIG_USB_SL811_BFIN_IRQ,
+		.start = IRQ_PF4,
+		.end = IRQ_PF4,
 		.flags = IORESOURCE_IRQ | IORESOURCE_IRQ_HIGHLEVEL,
 	},
 };