genirq: generic-chip: Export some irq_gc_ functions

When building imx_v6_v7_defconfig with imx-drm drivers selected as
modules, we get the following build errors:

ERROR: "irq_gc_mask_clr_bit" [drivers/staging/imx-drm/ipu-v3/imx-ipu-v3.ko] undefined!
ERROR: "irq_gc_mask_set_bit" [drivers/staging/imx-drm/ipu-v3/imx-ipu-v3.ko] undefined!
ERROR: "irq_gc_ack_set_bit" [drivers/staging/imx-drm/ipu-v3/imx-ipu-v3.ko] undefined!

Export the required functions to avoid this problem.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Cc: shawn.guo@linaro.org
Cc: kernel@pengutronix.de
Link: http://lkml.kernel.org/r/1372389789-7048-1-git-send-email-festevam@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/irq/generic-chip.c b/kernel/irq/generic-chip.c
index a746a8f..76ea748 100644
--- a/kernel/irq/generic-chip.c
+++ b/kernel/irq/generic-chip.c
@@ -62,6 +62,7 @@
 	irq_reg_writel(*ct->mask_cache, gc->reg_base + ct->regs.mask);
 	irq_gc_unlock(gc);
 }
+EXPORT_SYMBOL_GPL(irq_gc_mask_set_bit);
 
 /**
  * irq_gc_mask_set_mask_bit - Mask chip via clearing bit in mask register
@@ -81,6 +82,7 @@
 	irq_reg_writel(*ct->mask_cache, gc->reg_base + ct->regs.mask);
 	irq_gc_unlock(gc);
 }
+EXPORT_SYMBOL_GPL(irq_gc_mask_clr_bit);
 
 /**
  * irq_gc_unmask_enable_reg - Unmask chip via enable register
@@ -115,6 +117,7 @@
 	irq_reg_writel(mask, gc->reg_base + ct->regs.ack);
 	irq_gc_unlock(gc);
 }
+EXPORT_SYMBOL_GPL(irq_gc_ack_set_bit);
 
 /**
  * irq_gc_ack_clr_bit - Ack pending interrupt via clearing bit