kernel: add missing config symbol

Signed-off-by: Felix Fietkau <[email protected]>

target/linux/generic/config-4.4

@@ -3768,6 +3768,7 @@ CONFIG_SND_PCI=y
 # CONFIG_SND_PCM_OSS is not set
 CONFIG_SND_PCM_OSS_PLUGINS=y
 # CONFIG_SND_PCM_TIMER is not set
+# CONFIG_SND_PCM_XRUN_DEBUG is not set
 # CONFIG_SND_PCXHR is not set
 # CONFIG_SND_PDAUDIOCF is not set
 # CONFIG_SND_PORTMAN2X4 is not set