[source] kernel: fix kmod-sound-core build error

[LEDE Commits]

mkresin pushed a commit to source.git, branch master:
https://git.lede-project.org/578f7b9c597b0ea9bcf0726cc681713c0672edfe

commit 578f7b9c597b0ea9bcf0726cc681713c0672edfe
Author: Mathias Kresin <dev at kresin.me>
AuthorDate: Sat Nov 5 22:21:20 2016 +0100

    kernel: fix kmod-sound-core build error
    
    Fix build error introduced with 2ab6aac.
    
    Signed-off-by: Mathias Kresin <dev at kresin.me>
---
 package/kernel/linux/modules/sound.mk | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/package/kernel/linux/modules/sound.mk b/package/kernel/linux/modules/sound.mk
index 71765ed..de5d8fc 100644
--- a/package/kernel/linux/modules/sound.mk
+++ b/package/kernel/linux/modules/sound.mk
@@ -49,7 +49,7 @@ define KernelPackage/sound-core
 	CONFIG_SND_RAWMIDI \
 	CONFIG_SND_TIMER \
 	CONFIG_SND_PCM \
-	CONFIG_SND_PCM_TIMER \
+	CONFIG_SND_PCM_TIMER=y \
 	CONFIG_SND_SEQUENCER \
 	CONFIG_SND_VIRMIDI \
 	CONFIG_SND_SEQ_DUMMY \