staging: vchiq_2835_arm: revert "quit using custom down_interruptible()"

The killable version of down() is meant to be used on situations where
it should not fail at all costs, but still have the convenience of being
able to kill it if really necessary. VCHIQ doesn't fit this criteria, as
it's mainly used as an interface to V4L2 and ALSA devices.

Fixes: ff5979ad ("staging: vchiq_2835_arm: quit using custom down_interruptible()")
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c

@@ -514,7 +514,7 @@ create_pagelist(char __user *buf, size_t count, unsigned short type)
 		(g_cache_line_size - 1)))) {
 		char *fragments;
 
-		if (down_killable(&g_free_fragments_sema)) {
+		if (down_interruptible(&g_free_fragments_sema) != 0) {
 			cleanup_pagelistinfo(pagelistinfo);
 			return NULL;
 		}