powerpc/32: Add a missing include header

The header file <linux/syscalls.h> was missing from the includes. Fix the
following warning, treated as error with W=1:

  arch/powerpc/kernel/pci_32.c:286:6: error: no previous prototype for ‘sys_pciconfig_iobase’ [-Werror=missing-prototypes]
Signed-off-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/pci_32.c

@@ -11,6 +11,7 @@
 #include <linux/sched.h>
 #include <linux/errno.h>
 #include <linux/bootmem.h>
+#include <linux/syscalls.h>
 #include <linux/irq.h>
 #include <linux/list.h>
 #include <linux/of.h>