um: os-linux/mem.c needs sys/stat.h

The os-linux/mem.c file calls fchmod function, which is declared in sys/stat.h
header file, so include it. Fixes build breakage under FC13.

Signed-off-by: Liu Aleaxander <[e-mail]>
Acked-by: Boaz Harrosh <[e-mail]>
Cc: Jeff Dike <[e-mail]>
Cc: <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/um/os-Linux/mem.c

···
 #include <errno.h>
 #include <fcntl.h>
 #include <string.h>
+#include <sys/stat.h>
 #include <sys/mman.h>
 #include <sys/param.h>
 #include "init.h"