powerpc/powernv: Remove never used pnv_power9_force_smt4

This removes never used symbol - pnv_power9_force_smt4.

Note that we might still want to add stubs for:
	void pnv_power9_force_smt4_catch(void);
	void pnv_power9_force_smt4_release(void);

Fixes: 7672691a "powerpc/powernv: Provide a way to force a core into SMT4 mode"
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/powernv.h

@@ -40,7 +40,6 @@ static inline int pnv_npu2_handle_fault(struct npu_context *context,
 }
 
 static inline void pnv_tm_init(void) { }
-static inline void pnv_power9_force_smt4(void) { }
 #endif
 
 #endif /* _ASM_POWERNV_H */