staging: goldfish: audio: fix compiliation on arm

BugLink: https://bugs.launchpad.net/bugs/1826212

[ Upstream commit 45321507 ]

We do actually need slab.h, by luck we get it on other platforms but not
always on ARM. Include it properly.
Signed-off-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Jin Qian <jinqian@android.com>
Signed-off-by: Alan <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/staging/goldfish/goldfish_audio.c

@@ -26,6 +26,7 @@
 #include <linux/sched.h>
 #include <linux/dma-mapping.h>
 #include <linux/uaccess.h>
+#include <linux/slab.h>
 #include <linux/goldfish.h>
 
 MODULE_AUTHOR("Google, Inc.");