powerpc: Remove second definition of STACK_FRAME_OVERHEAD

Since STACK_FRAME_OVERHEAD is defined in asm/ptrace.h and that
is ASSEMBER safe, we can just include that instead of going via
asm-offsets.h.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/misc_64.S

@@ -25,6 +25,7 @@
 #include <asm/cputable.h>
 #include <asm/thread_info.h>
 #include <asm/kexec.h>
+#include <asm/ptrace.h>
 
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