powerpc/32: Avoid #ifdef nested with FTR_SECTION on booke syscall entry

On booke, SYSCALL_ENTRY macro nests an FTR_SECTION with a #ifdef
CONFIG_KVM_BOOKE_HV.

Duplicate the single instruction alternative to avoid nesting.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/33db61d5f85146262dbe26648f8f87eca3cae393.1622818435.git.christophe.leroy@csgroup.eu

arch/powerpc/kernel/head_booke.h

@@ -128,10 +128,10 @@ BEGIN_FTR_SECTION
 	mr	r12, r13
 	lwz	r13, THREAD_NORMSAVE(2)(r10)
 FTR_SECTION_ELSE
-#endif
 	mfcr	r12
-#ifdef CONFIG_KVM_BOOKE_HV
 ALT_FTR_SECTION_END_IFSET(CPU_FTR_EMB_HV)
+#else
+	mfcr	r12
 #endif
 	mfspr	r9, SPRN_SRR1
 	BOOKE_CLEAR_BTB(r11)