powerpc: Fix various compile errors with ARCH=ppc, ppc64 and powerpc

This makes ppc use the syscalls.c from arch/powerpc/kernel, exports
copy_and_flush from head_32.S for use by prom_init.c (ARCH=powerpc),
and consolidates the sys_fadvise64_64 implementations for 32-bit.

Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
index 3e3a4f6..7a23721 100644
--- a/arch/powerpc/kernel/syscalls.c
+++ b/arch/powerpc/kernel/syscalls.c
@@ -336,6 +336,13 @@
 }
 #endif
 
+long ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low,
+		      u32 len_high, u32 len_low)
+{
+	return sys_fadvise64(fd, (u64)offset_high << 32 | offset_low,
+			     (u64)len_high << 32 | len_low, advice);
+}
+
 void do_show_syscall(unsigned long r3, unsigned long r4, unsigned long r5,
 		     unsigned long r6, unsigned long r7, unsigned long r8,
 		     struct pt_regs *regs)