ANDROID: proc: fix config & includes for /proc/uid

Per-UID proc files require rtmutex, so add an include statement and
make CONFIG_PROC_UID depend on CONFIG_RT_MUTEXES

Bug: 74338318
Test: Previously broken bcm63xx and stm32 builds now succeed.
Change-Id: Id9d44775cf9ea04319d21d833a4666e3dfc16b40
Signed-off-by: Connor O'Brien <connoro@google.com>

fs/proc/Kconfig

@@ -85,6 +85,6 @@ config PROC_CHILDREN
 config PROC_UID
 	bool "Include /proc/uid/ files"
 	default y
-	depends on PROC_FS
+	depends on PROC_FS && RT_MUTEXES
 	help
 	Provides aggregated per-uid information under /proc/uid.

fs/proc/uid.c

@@ -7,6 +7,7 @@
 #include <linux/hashtable.h>
 #include <linux/init.h>
 #include <linux/proc_fs.h>
+#include <linux/rtmutex.h>
 #include <linux/sched.h>
 #include <linux/seq_file.h>
 #include <linux/slab.h>