powerpc/64/sstep: Ifdef the deprecated fast endian switch syscall

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200225173541.1549955-25-npiggin@gmail.com

arch/powerpc/lib/sstep.c

@@ -3179,8 +3179,9 @@ int emulate_step(struct pt_regs *regs, unsigned int instr)
 		 * entry code works.  If that is changed, this will
 		 * need to be changed also.
 		 */
-		if (regs->gpr[0] == 0x1ebe &&
-		    cpu_has_feature(CPU_FTR_REAL_LE)) {
+		if (IS_ENABLED(CONFIG_PPC_FAST_ENDIAN_SWITCH) &&
+				cpu_has_feature(CPU_FTR_REAL_LE) &&
+				regs->gpr[0] == 0x1ebe) {
 			regs->msr ^= MSR_LE;
 			goto instr_done;
 		}